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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "chrome/browser/extensions/chrome_app_sorting.h"
      6 
      7 #include <algorithm>
      8 #include <vector>
      9 
     10 #include "chrome/browser/chrome_notification_types.h"
     11 #include "chrome/browser/extensions/extension_scoped_prefs.h"
     12 #include "chrome/browser/extensions/extension_sync_service.h"
     13 #include "chrome/common/extensions/extension_constants.h"
     14 #include "content/public/browser/notification_service.h"
     15 #include "extensions/common/extension.h"
     16 
     17 #if defined(OS_CHROMEOS)
     18 #include "chrome/browser/chromeos/extensions/default_app_order.h"
     19 #endif
     20 
     21 namespace extensions {
     22 
     23 namespace {
     24 
     25 // The number of apps per page. This isn't a hard limit, but new apps installed
     26 // from the webstore will overflow onto a new page if this limit is reached.
     27 const size_t kNaturalAppPageSize = 18;
     28 
     29 // A preference determining the order of which the apps appear on the NTP.
     30 const char kPrefAppLaunchIndexDeprecated[] = "app_launcher_index";
     31 const char kPrefAppLaunchOrdinal[] = "app_launcher_ordinal";
     32 
     33 // A preference determining the page on which an app appears in the NTP.
     34 const char kPrefPageIndexDeprecated[] = "page_index";
     35 const char kPrefPageOrdinal[] = "page_ordinal";
     36 
     37 }  // namespace
     38 
     39 ////////////////////////////////////////////////////////////////////////////////
     40 // ChromeAppSorting::AppOrdinals
     41 
     42 ChromeAppSorting::AppOrdinals::AppOrdinals() {}
     43 
     44 ChromeAppSorting::AppOrdinals::~AppOrdinals() {}
     45 
     46 ////////////////////////////////////////////////////////////////////////////////
     47 // ChromeAppSorting
     48 
     49 ChromeAppSorting::ChromeAppSorting()
     50     : extension_scoped_prefs_(NULL),
     51       extension_sync_service_(NULL),
     52       default_ordinals_created_(false) {
     53 }
     54 
     55 ChromeAppSorting::~ChromeAppSorting() {
     56 }
     57 
     58 void ChromeAppSorting::SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) {
     59   extension_scoped_prefs_ = prefs;
     60 }
     61 
     62 void ChromeAppSorting::SetExtensionSyncService(
     63     ExtensionSyncService* extension_sync_service) {
     64   extension_sync_service_ = extension_sync_service;
     65 }
     66 
     67 void ChromeAppSorting::Initialize(
     68     const extensions::ExtensionIdList& extension_ids) {
     69   InitializePageOrdinalMap(extension_ids);
     70 
     71   MigrateAppIndex(extension_ids);
     72 }
     73 
     74 void ChromeAppSorting::CreateOrdinalsIfNecessary(size_t minimum_size) {
     75   // Create StringOrdinal values as required to ensure |ntp_ordinal_map_| has at
     76   // least |minimum_size| entries.
     77   if (ntp_ordinal_map_.empty() && minimum_size > 0)
     78     ntp_ordinal_map_[syncer::StringOrdinal::CreateInitialOrdinal()];
     79 
     80   while (ntp_ordinal_map_.size() < minimum_size) {
     81     syncer::StringOrdinal filler =
     82         ntp_ordinal_map_.rbegin()->first.CreateAfter();
     83     AppLaunchOrdinalMap empty_ordinal_map;
     84     ntp_ordinal_map_.insert(std::make_pair(filler, empty_ordinal_map));
     85   }
     86 }
     87 
     88 void ChromeAppSorting::MigrateAppIndex(
     89     const extensions::ExtensionIdList& extension_ids) {
     90   if (extension_ids.empty())
     91     return;
     92 
     93   // Convert all the page index values to page ordinals. If there are any
     94   // app launch values that need to be migrated, inserted them into a sorted
     95   // set to be dealt with later.
     96   typedef std::map<syncer::StringOrdinal, std::map<int, const std::string*>,
     97                    syncer::StringOrdinal::LessThanFn> AppPositionToIdMapping;
     98   AppPositionToIdMapping app_launches_to_convert;
     99   for (extensions::ExtensionIdList::const_iterator ext_id =
    100            extension_ids.begin(); ext_id != extension_ids.end(); ++ext_id) {
    101     int old_page_index = 0;
    102     syncer::StringOrdinal page = GetPageOrdinal(*ext_id);
    103     if (extension_scoped_prefs_->ReadPrefAsInteger(
    104             *ext_id,
    105             kPrefPageIndexDeprecated,
    106             &old_page_index)) {
    107       // Some extensions have invalid page index, so we don't
    108       // attempt to convert them.
    109       if (old_page_index < 0) {
    110         DLOG(WARNING) << "Extension " << *ext_id
    111                       << " has an invalid page index " << old_page_index
    112                       << ". Aborting attempt to convert its index.";
    113         break;
    114       }
    115 
    116       CreateOrdinalsIfNecessary(static_cast<size_t>(old_page_index) + 1);
    117 
    118       page = PageIntegerAsStringOrdinal(old_page_index);
    119       SetPageOrdinal(*ext_id, page);
    120       extension_scoped_prefs_->UpdateExtensionPref(
    121           *ext_id, kPrefPageIndexDeprecated, NULL);
    122     }
    123 
    124     int old_app_launch_index = 0;
    125     if (extension_scoped_prefs_->ReadPrefAsInteger(
    126             *ext_id,
    127             kPrefAppLaunchIndexDeprecated,
    128             &old_app_launch_index)) {
    129       // We can't update the app launch index value yet, because we use
    130       // GetNextAppLaunchOrdinal to get the new ordinal value and it requires
    131       // all the ordinals with lower values to have already been migrated.
    132       // A valid page ordinal is also required because otherwise there is
    133       // no page to add the app to.
    134       if (page.IsValid())
    135         app_launches_to_convert[page][old_app_launch_index] = &*ext_id;
    136 
    137       extension_scoped_prefs_->UpdateExtensionPref(
    138           *ext_id, kPrefAppLaunchIndexDeprecated, NULL);
    139     }
    140   }
    141 
    142   // Remove any empty pages that may have been added. This shouldn't occur,
    143   // but double check here to prevent future problems with conversions between
    144   // integers and StringOrdinals.
    145   for (PageOrdinalMap::iterator it = ntp_ordinal_map_.begin();
    146        it != ntp_ordinal_map_.end();) {
    147     if (it->second.empty()) {
    148       PageOrdinalMap::iterator prev_it = it;
    149       ++it;
    150       ntp_ordinal_map_.erase(prev_it);
    151     } else {
    152       ++it;
    153     }
    154   }
    155 
    156   if (app_launches_to_convert.empty())
    157     return;
    158 
    159   // Create the new app launch ordinals and remove the old preferences. Since
    160   // the set is sorted, each time we migrate an apps index, we know that all of
    161   // the remaining apps will appear further down the NTP than it or on a
    162   // different page.
    163   for (AppPositionToIdMapping::const_iterator page_it =
    164            app_launches_to_convert.begin();
    165        page_it != app_launches_to_convert.end(); ++page_it) {
    166     syncer::StringOrdinal page = page_it->first;
    167     for (std::map<int, const std::string*>::const_iterator launch_it =
    168             page_it->second.begin(); launch_it != page_it->second.end();
    169         ++launch_it) {
    170       SetAppLaunchOrdinal(*(launch_it->second),
    171                           CreateNextAppLaunchOrdinal(page));
    172     }
    173   }
    174 }
    175 
    176 void ChromeAppSorting::FixNTPOrdinalCollisions() {
    177   for (PageOrdinalMap::iterator page_it = ntp_ordinal_map_.begin();
    178        page_it != ntp_ordinal_map_.end(); ++page_it) {
    179     AppLaunchOrdinalMap& page = page_it->second;
    180 
    181     AppLaunchOrdinalMap::iterator app_launch_it = page.begin();
    182     while (app_launch_it != page.end()) {
    183       int app_count = page.count(app_launch_it->first);
    184       if (app_count == 1) {
    185         ++app_launch_it;
    186         continue;
    187       }
    188 
    189       syncer::StringOrdinal repeated_ordinal = app_launch_it->first;
    190 
    191       // Sort the conflicting keys by their extension id, this is how
    192       // the order is decided.
    193       std::vector<std::string> conflicting_ids;
    194       for (int i = 0; i < app_count; ++i, ++app_launch_it)
    195         conflicting_ids.push_back(app_launch_it->second);
    196       std::sort(conflicting_ids.begin(), conflicting_ids.end());
    197 
    198       syncer::StringOrdinal upper_bound_ordinal = app_launch_it == page.end() ?
    199           syncer::StringOrdinal() :
    200           app_launch_it->first;
    201       syncer::StringOrdinal lower_bound_ordinal = repeated_ordinal;
    202 
    203       // Start at position 1 because the first extension can keep the conflicted
    204       // value.
    205       for (int i = 1; i < app_count; ++i) {
    206         syncer::StringOrdinal unique_app_launch;
    207         if (upper_bound_ordinal.IsValid()) {
    208           unique_app_launch =
    209               lower_bound_ordinal.CreateBetween(upper_bound_ordinal);
    210         } else {
    211           unique_app_launch = lower_bound_ordinal.CreateAfter();
    212         }
    213 
    214         SetAppLaunchOrdinal(conflicting_ids[i], unique_app_launch);
    215         lower_bound_ordinal = unique_app_launch;
    216       }
    217     }
    218   }
    219 
    220   content::NotificationService::current()->Notify(
    221       chrome::NOTIFICATION_EXTENSION_LAUNCHER_REORDERED,
    222       content::Source<ChromeAppSorting>(this),
    223       content::NotificationService::NoDetails());
    224 }
    225 
    226 void ChromeAppSorting::EnsureValidOrdinals(
    227     const std::string& extension_id,
    228     const syncer::StringOrdinal& suggested_page) {
    229   syncer::StringOrdinal page_ordinal = GetPageOrdinal(extension_id);
    230   if (!page_ordinal.IsValid()) {
    231     if (suggested_page.IsValid()) {
    232       page_ordinal = suggested_page;
    233     } else if (!GetDefaultOrdinals(extension_id, &page_ordinal, NULL) ||
    234         !page_ordinal.IsValid()) {
    235       page_ordinal = GetNaturalAppPageOrdinal();
    236     }
    237 
    238     SetPageOrdinal(extension_id, page_ordinal);
    239   }
    240 
    241   syncer::StringOrdinal app_launch_ordinal = GetAppLaunchOrdinal(extension_id);
    242   if (!app_launch_ordinal.IsValid()) {
    243     // If using default app launcher ordinal, make sure there is no collision.
    244     if (GetDefaultOrdinals(extension_id, NULL, &app_launch_ordinal) &&
    245         app_launch_ordinal.IsValid())
    246       app_launch_ordinal = ResolveCollision(page_ordinal, app_launch_ordinal);
    247     else
    248       app_launch_ordinal = CreateNextAppLaunchOrdinal(page_ordinal);
    249 
    250     SetAppLaunchOrdinal(extension_id, app_launch_ordinal);
    251   }
    252 }
    253 
    254 void ChromeAppSorting::OnExtensionMoved(
    255     const std::string& moved_extension_id,
    256     const std::string& predecessor_extension_id,
    257     const std::string& successor_extension_id) {
    258   // We only need to change the StringOrdinal if there are neighbours.
    259   if (!predecessor_extension_id.empty() || !successor_extension_id.empty()) {
    260     if (predecessor_extension_id.empty()) {
    261       // Only a successor.
    262       SetAppLaunchOrdinal(
    263           moved_extension_id,
    264           GetAppLaunchOrdinal(successor_extension_id).CreateBefore());
    265     } else if (successor_extension_id.empty()) {
    266       // Only a predecessor.
    267       SetAppLaunchOrdinal(
    268           moved_extension_id,
    269           GetAppLaunchOrdinal(predecessor_extension_id).CreateAfter());
    270     } else {
    271       // Both a successor and predecessor
    272       const syncer::StringOrdinal& predecessor_ordinal =
    273           GetAppLaunchOrdinal(predecessor_extension_id);
    274       const syncer::StringOrdinal& successor_ordinal =
    275           GetAppLaunchOrdinal(successor_extension_id);
    276       SetAppLaunchOrdinal(moved_extension_id,
    277                           predecessor_ordinal.CreateBetween(successor_ordinal));
    278     }
    279   }
    280 
    281   content::NotificationService::current()->Notify(
    282       chrome::NOTIFICATION_EXTENSION_LAUNCHER_REORDERED,
    283       content::Source<ChromeAppSorting>(this),
    284       content::Details<const std::string>(&moved_extension_id));
    285 }
    286 
    287 
    288 syncer::StringOrdinal ChromeAppSorting::GetAppLaunchOrdinal(
    289     const std::string& extension_id) const {
    290   std::string raw_value;
    291   // If the preference read fails then raw_value will still be unset and we
    292   // will return an invalid StringOrdinal to signal that no app launch ordinal
    293   // was found.
    294   extension_scoped_prefs_->ReadPrefAsString(
    295       extension_id, kPrefAppLaunchOrdinal, &raw_value);
    296   return syncer::StringOrdinal(raw_value);
    297 }
    298 
    299 void ChromeAppSorting::SetAppLaunchOrdinal(
    300     const std::string& extension_id,
    301     const syncer::StringOrdinal& new_app_launch_ordinal) {
    302   // No work is required if the old and new values are the same.
    303   if (new_app_launch_ordinal.EqualsOrBothInvalid(
    304           GetAppLaunchOrdinal(extension_id))) {
    305     return;
    306   }
    307 
    308   syncer::StringOrdinal page_ordinal = GetPageOrdinal(extension_id);
    309   RemoveOrdinalMapping(
    310       extension_id, page_ordinal, GetAppLaunchOrdinal(extension_id));
    311   AddOrdinalMapping(extension_id, page_ordinal, new_app_launch_ordinal);
    312 
    313   Value* new_value = new_app_launch_ordinal.IsValid() ?
    314       new base::StringValue(new_app_launch_ordinal.ToInternalValue()) :
    315       NULL;
    316 
    317   extension_scoped_prefs_->UpdateExtensionPref(
    318       extension_id,
    319       kPrefAppLaunchOrdinal,
    320       new_value);
    321   SyncIfNeeded(extension_id);
    322 }
    323 
    324 syncer::StringOrdinal ChromeAppSorting::CreateFirstAppLaunchOrdinal(
    325     const syncer::StringOrdinal& page_ordinal) const {
    326   const syncer::StringOrdinal& min_ordinal =
    327       GetMinOrMaxAppLaunchOrdinalsOnPage(page_ordinal,
    328                                          ChromeAppSorting::MIN_ORDINAL);
    329 
    330   if (min_ordinal.IsValid())
    331     return min_ordinal.CreateBefore();
    332   else
    333     return syncer::StringOrdinal::CreateInitialOrdinal();
    334 }
    335 
    336 syncer::StringOrdinal ChromeAppSorting::CreateNextAppLaunchOrdinal(
    337     const syncer::StringOrdinal& page_ordinal) const {
    338   const syncer::StringOrdinal& max_ordinal =
    339       GetMinOrMaxAppLaunchOrdinalsOnPage(page_ordinal,
    340                                          ChromeAppSorting::MAX_ORDINAL);
    341 
    342   if (max_ordinal.IsValid())
    343     return max_ordinal.CreateAfter();
    344   else
    345     return syncer::StringOrdinal::CreateInitialOrdinal();
    346 }
    347 
    348 syncer::StringOrdinal ChromeAppSorting::CreateFirstAppPageOrdinal() const {
    349   if (ntp_ordinal_map_.empty())
    350     return syncer::StringOrdinal::CreateInitialOrdinal();
    351 
    352   return ntp_ordinal_map_.begin()->first;
    353 }
    354 
    355 syncer::StringOrdinal ChromeAppSorting::GetNaturalAppPageOrdinal() const {
    356   if (ntp_ordinal_map_.empty())
    357     return syncer::StringOrdinal::CreateInitialOrdinal();
    358 
    359   for (PageOrdinalMap::const_iterator it = ntp_ordinal_map_.begin();
    360        it != ntp_ordinal_map_.end(); ++it) {
    361     if (CountItemsVisibleOnNtp(it->second) < kNaturalAppPageSize)
    362       return it->first;
    363   }
    364 
    365   // Add a new page as all existing pages are full.
    366   syncer::StringOrdinal last_element = ntp_ordinal_map_.rbegin()->first;
    367   return last_element.CreateAfter();
    368 }
    369 
    370 syncer::StringOrdinal ChromeAppSorting::GetPageOrdinal(
    371     const std::string& extension_id) const {
    372   std::string raw_data;
    373   // If the preference read fails then raw_data will still be unset and we will
    374   // return an invalid StringOrdinal to signal that no page ordinal was found.
    375   extension_scoped_prefs_->ReadPrefAsString(
    376       extension_id, kPrefPageOrdinal, &raw_data);
    377   return syncer::StringOrdinal(raw_data);
    378 }
    379 
    380 void ChromeAppSorting::SetPageOrdinal(
    381     const std::string& extension_id,
    382     const syncer::StringOrdinal& new_page_ordinal) {
    383   // No work is required if the old and new values are the same.
    384   if (new_page_ordinal.EqualsOrBothInvalid(GetPageOrdinal(extension_id)))
    385     return;
    386 
    387   syncer::StringOrdinal app_launch_ordinal = GetAppLaunchOrdinal(extension_id);
    388   RemoveOrdinalMapping(
    389       extension_id, GetPageOrdinal(extension_id), app_launch_ordinal);
    390   AddOrdinalMapping(extension_id, new_page_ordinal, app_launch_ordinal);
    391 
    392   Value* new_value = new_page_ordinal.IsValid() ?
    393       new base::StringValue(new_page_ordinal.ToInternalValue()) :
    394       NULL;
    395 
    396   extension_scoped_prefs_->UpdateExtensionPref(
    397       extension_id,
    398       kPrefPageOrdinal,
    399       new_value);
    400   SyncIfNeeded(extension_id);
    401 }
    402 
    403 void ChromeAppSorting::ClearOrdinals(const std::string& extension_id) {
    404   RemoveOrdinalMapping(extension_id,
    405                        GetPageOrdinal(extension_id),
    406                        GetAppLaunchOrdinal(extension_id));
    407 
    408   extension_scoped_prefs_->UpdateExtensionPref(
    409       extension_id, kPrefPageOrdinal, NULL);
    410   extension_scoped_prefs_->UpdateExtensionPref(
    411       extension_id, kPrefAppLaunchOrdinal, NULL);
    412 }
    413 
    414 int ChromeAppSorting::PageStringOrdinalAsInteger(
    415     const syncer::StringOrdinal& page_ordinal) const {
    416   if (!page_ordinal.IsValid())
    417     return -1;
    418 
    419   PageOrdinalMap::const_iterator it = ntp_ordinal_map_.find(page_ordinal);
    420   return it != ntp_ordinal_map_.end() ?
    421       std::distance(ntp_ordinal_map_.begin(), it) : -1;
    422 }
    423 
    424 syncer::StringOrdinal ChromeAppSorting::PageIntegerAsStringOrdinal(
    425     size_t page_index) {
    426   if (page_index < ntp_ordinal_map_.size()) {
    427     PageOrdinalMap::const_iterator it = ntp_ordinal_map_.begin();
    428     std::advance(it, page_index);
    429     return it->first;
    430   }
    431 
    432   CreateOrdinalsIfNecessary(page_index + 1);
    433   return ntp_ordinal_map_.rbegin()->first;
    434 }
    435 
    436 void ChromeAppSorting::MarkExtensionAsHidden(const std::string& extension_id) {
    437   ntp_hidden_extensions_.insert(extension_id);
    438 }
    439 
    440 syncer::StringOrdinal ChromeAppSorting::GetMinOrMaxAppLaunchOrdinalsOnPage(
    441     const syncer::StringOrdinal& target_page_ordinal,
    442     AppLaunchOrdinalReturn return_type) const {
    443   CHECK(target_page_ordinal.IsValid());
    444 
    445   syncer::StringOrdinal return_value;
    446 
    447   PageOrdinalMap::const_iterator page =
    448       ntp_ordinal_map_.find(target_page_ordinal);
    449   if (page != ntp_ordinal_map_.end()) {
    450     const AppLaunchOrdinalMap& app_list = page->second;
    451 
    452     if (app_list.empty())
    453       return syncer::StringOrdinal();
    454 
    455     if (return_type == ChromeAppSorting::MAX_ORDINAL)
    456       return_value = app_list.rbegin()->first;
    457     else if (return_type == ChromeAppSorting::MIN_ORDINAL)
    458       return_value = app_list.begin()->first;
    459   }
    460 
    461   return return_value;
    462 }
    463 
    464 void ChromeAppSorting::InitializePageOrdinalMap(
    465     const extensions::ExtensionIdList& extension_ids) {
    466   for (extensions::ExtensionIdList::const_iterator ext_it =
    467            extension_ids.begin(); ext_it != extension_ids.end(); ++ext_it) {
    468     AddOrdinalMapping(*ext_it,
    469                       GetPageOrdinal(*ext_it),
    470                       GetAppLaunchOrdinal(*ext_it));
    471 
    472     // Ensure that the web store app still isn't found in this list, since
    473     // it is added after this loop.
    474     DCHECK(*ext_it != extension_misc::kWebStoreAppId);
    475     DCHECK(*ext_it != extension_misc::kChromeAppId);
    476   }
    477 
    478   // Include the Web Store App since it is displayed on the NTP.
    479   syncer::StringOrdinal web_store_app_page =
    480       GetPageOrdinal(extension_misc::kWebStoreAppId);
    481   if (web_store_app_page.IsValid()) {
    482     AddOrdinalMapping(extension_misc::kWebStoreAppId,
    483                       web_store_app_page,
    484                       GetAppLaunchOrdinal(extension_misc::kWebStoreAppId));
    485   }
    486   // Include the Chrome App since it is displayed in the app launcher.
    487   syncer::StringOrdinal chrome_app_page =
    488       GetPageOrdinal(extension_misc::kChromeAppId);
    489   if (chrome_app_page.IsValid()) {
    490     AddOrdinalMapping(extension_misc::kChromeAppId,
    491                       chrome_app_page,
    492                       GetAppLaunchOrdinal(extension_misc::kChromeAppId));
    493   }
    494 }
    495 
    496 void ChromeAppSorting::AddOrdinalMapping(
    497     const std::string& extension_id,
    498     const syncer::StringOrdinal& page_ordinal,
    499     const syncer::StringOrdinal& app_launch_ordinal) {
    500   if (!page_ordinal.IsValid() || !app_launch_ordinal.IsValid())
    501     return;
    502 
    503   ntp_ordinal_map_[page_ordinal].insert(
    504       std::make_pair(app_launch_ordinal, extension_id));
    505 }
    506 
    507 void ChromeAppSorting::RemoveOrdinalMapping(
    508     const std::string& extension_id,
    509     const syncer::StringOrdinal& page_ordinal,
    510     const syncer::StringOrdinal& app_launch_ordinal) {
    511   if (!page_ordinal.IsValid() || !app_launch_ordinal.IsValid())
    512     return;
    513 
    514   // Check that the page exists using find to prevent creating a new page
    515   // if |page_ordinal| isn't a used page.
    516   PageOrdinalMap::iterator page_map = ntp_ordinal_map_.find(page_ordinal);
    517   if (page_map == ntp_ordinal_map_.end())
    518     return;
    519 
    520   for (AppLaunchOrdinalMap::iterator it =
    521            page_map->second.find(app_launch_ordinal);
    522        it != page_map->second.end(); ++it) {
    523     if (it->second == extension_id) {
    524       page_map->second.erase(it);
    525       break;
    526     }
    527   }
    528 }
    529 
    530 void ChromeAppSorting::SyncIfNeeded(const std::string& extension_id) {
    531   if (extension_sync_service_)
    532     extension_sync_service_->SyncOrderingChange(extension_id);
    533 }
    534 
    535 void ChromeAppSorting::CreateDefaultOrdinals() {
    536   if (default_ordinals_created_)
    537     return;
    538   default_ordinals_created_ = true;
    539 
    540   // The following defines the default order of apps.
    541 #if defined(OS_CHROMEOS)
    542   std::vector<std::string> app_ids;
    543   chromeos::default_app_order::Get(&app_ids);
    544 #else
    545   const char* kDefaultAppOrder[] = {
    546     extension_misc::kChromeAppId,
    547     extension_misc::kWebStoreAppId,
    548   };
    549   const std::vector<const char*> app_ids(
    550       kDefaultAppOrder, kDefaultAppOrder + arraysize(kDefaultAppOrder));
    551 #endif
    552 
    553   syncer::StringOrdinal page_ordinal = CreateFirstAppPageOrdinal();
    554   syncer::StringOrdinal app_launch_ordinal =
    555       CreateFirstAppLaunchOrdinal(page_ordinal);
    556   for (size_t i = 0; i < app_ids.size(); ++i) {
    557     const std::string extension_id = app_ids[i];
    558     default_ordinals_[extension_id].page_ordinal = page_ordinal;
    559     default_ordinals_[extension_id].app_launch_ordinal = app_launch_ordinal;
    560     app_launch_ordinal = app_launch_ordinal.CreateAfter();
    561   }
    562 }
    563 
    564 bool ChromeAppSorting::GetDefaultOrdinals(
    565     const std::string& extension_id,
    566     syncer::StringOrdinal* page_ordinal,
    567     syncer::StringOrdinal* app_launch_ordinal) {
    568   CreateDefaultOrdinals();
    569   AppOrdinalsMap::const_iterator it = default_ordinals_.find(extension_id);
    570   if (it == default_ordinals_.end())
    571     return false;
    572 
    573   if (page_ordinal)
    574     *page_ordinal = it->second.page_ordinal;
    575   if (app_launch_ordinal)
    576     *app_launch_ordinal = it->second.app_launch_ordinal;
    577   return true;
    578 }
    579 
    580 syncer::StringOrdinal ChromeAppSorting::ResolveCollision(
    581     const syncer::StringOrdinal& page_ordinal,
    582     const syncer::StringOrdinal& app_launch_ordinal) const {
    583   DCHECK(page_ordinal.IsValid() && app_launch_ordinal.IsValid());
    584 
    585   PageOrdinalMap::const_iterator page_it = ntp_ordinal_map_.find(page_ordinal);
    586   if (page_it == ntp_ordinal_map_.end())
    587     return app_launch_ordinal;
    588 
    589   const AppLaunchOrdinalMap& page = page_it->second;
    590   AppLaunchOrdinalMap::const_iterator app_it = page.find(app_launch_ordinal);
    591   if (app_it == page.end())
    592     return app_launch_ordinal;
    593 
    594   // Finds the next app launcher ordinal. This is done by the following loop
    595   // because this function could be called before FixNTPOrdinalCollisions and
    596   // thus |page| might contains multiple entries with the same app launch
    597   // ordinal. See http://crbug.com/155603
    598   while (app_it != page.end() && app_launch_ordinal.Equals(app_it->first))
    599     ++app_it;
    600 
    601   // If there is no next after the collision, returns the next ordinal.
    602   if (app_it == page.end())
    603     return app_launch_ordinal.CreateAfter();
    604 
    605   // Otherwise, returns the ordinal between the collision and the next ordinal.
    606   return app_launch_ordinal.CreateBetween(app_it->first);
    607 }
    608 
    609 size_t ChromeAppSorting::CountItemsVisibleOnNtp(
    610     const AppLaunchOrdinalMap& m) const {
    611   size_t result = 0;
    612   for (AppLaunchOrdinalMap::const_iterator it = m.begin(); it != m.end();
    613        ++it) {
    614     const std::string& id = it->second;
    615     if (ntp_hidden_extensions_.count(id) == 0)
    616       result++;
    617   }
    618   return result;
    619 }
    620 
    621 }  // namespace extensions
    622