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      1 // Copyright (c) 2012 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/metrics/field_trial_synchronizer.h"
      6 
      7 #include "base/bind.h"
      8 #include "base/logging.h"
      9 #include "base/threading/thread.h"
     10 #include "chrome/common/chrome_constants.h"
     11 #include "chrome/common/render_messages.h"
     12 #include "chrome/common/variations/variations_util.h"
     13 #include "content/public/browser/browser_thread.h"
     14 #include "content/public/browser/render_process_host.h"
     15 
     16 using content::BrowserThread;
     17 
     18 namespace {
     19 
     20 // This singleton instance should be constructed during the single threaded
     21 // portion of main(). It initializes globals to provide support for all future
     22 // calls. This object is created on the UI thread, and it is destroyed after
     23 // all the other threads have gone away.
     24 FieldTrialSynchronizer* g_field_trial_synchronizer = NULL;
     25 
     26 }  // namespace
     27 
     28 FieldTrialSynchronizer::FieldTrialSynchronizer() {
     29   DCHECK(g_field_trial_synchronizer == NULL);
     30   g_field_trial_synchronizer = this;
     31   base::FieldTrialList::AddObserver(this);
     32 
     33   chrome_variations::SetChildProcessLoggingVariationList();
     34 }
     35 
     36 void FieldTrialSynchronizer::NotifyAllRenderers(
     37     const std::string& field_trial_name,
     38     const std::string& group_name) {
     39   // To iterate over RenderProcessHosts, or to send messages to the hosts, we
     40   // need to be on the UI thread.
     41   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
     42 
     43   for (content::RenderProcessHost::iterator it(
     44           content::RenderProcessHost::AllHostsIterator());
     45        !it.IsAtEnd(); it.Advance()) {
     46     it.GetCurrentValue()->Send(
     47         new ChromeViewMsg_SetFieldTrialGroup(field_trial_name, group_name));
     48   }
     49 }
     50 
     51 void FieldTrialSynchronizer::OnFieldTrialGroupFinalized(
     52     const std::string& field_trial_name,
     53     const std::string& group_name) {
     54   CHECK(!field_trial_name.empty() && !group_name.empty());
     55   BrowserThread::PostTask(
     56       BrowserThread::UI, FROM_HERE,
     57       base::Bind(&FieldTrialSynchronizer::NotifyAllRenderers,
     58                  this,
     59                  field_trial_name,
     60                  group_name));
     61   chrome_variations::SetChildProcessLoggingVariationList();
     62 }
     63 
     64 FieldTrialSynchronizer::~FieldTrialSynchronizer() {
     65   base::FieldTrialList::RemoveObserver(this);
     66   g_field_trial_synchronizer = NULL;
     67 }
     68