The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9f40b3589f58581858b7df56cde16d514943a4af

commit 9f40b3589f58581858b7df56cde16d514943a4af
Author: Christopher Cameron <ccameron@chromium.org>
Date: Thu Nov 02 16:53:52 2017

Allow sampling GL_RGBA16F from GLES2 compositor contexts

WebGL2 (ES3) requires that the internal format of half-float formats be
sized (GL_RGBA16F, for instance).

Compositor contexts (ES2) have an un-sized internal format (GL_RGBA).

This becomes problematic when WebGL2 generates a backbuffer that is to
be consumed by the compositor. In particular, we fail
Texture::TextureFilterable because the sized internal format GL_RGBA16F
is unknown to the compositor context.

Add an exception to the list of exceptions in the helper function to
checked size format support.

Bug:  777750 
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ib4afd4092ff15e4810bf3976b61321c6ede66693
Reviewed-on: https://chromium-review.googlesource.com/741082
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513519}
[modify] https://crrev.com/9f40b3589f58581858b7df56cde16d514943a4af/gpu/command_buffer/service/texture_manager.cc