Cross Reference: /external/pdfium/testing/image_diff

`Name`	`Date`	`Size`
Up to higher level directory
`DEPS`	21-Aug-2018	`71`
`image_diff.cpp`	21-Aug-2018	`10.2K`
`image_diff_png.cpp`	21-Aug-2018	`21.9K`
`image_diff_png.h`	21-Aug-2018	`1.6K`