Preserve alpha channel of 1.0 when emulating RGB back buffer.

content/test/gpu/gpu_tests/pixel_test_pages.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 class PixelTestPage(object):
   """A wrapper class mimicking the functionality of the PixelTestsStorySet
   from the old-style GPU tests.
   """
   def __init__(self, url, name, test_rect, revision,
                tolerance=2, browser_args=None, expected_colors=None):
@@ skipping 73 matching lines @@
       test_rect=[0, 0, 300, 300],
       revision=1),
 
     PixelTestPage(
       'pixel_webgl_noalpha_implicit_clear.html',
       base_name + '_WebGLTransparentGreenTriangle_NoAlpha_ImplicitClear',
       test_rect=[0, 0, 300, 300],
       revision=1),
 
     PixelTestPage(
+      'pixel_webgl2_blitframebuffer_noalpha.html',
+      base_name + '_WebGL2_BlitFramebuffer_NoAlpha',
+      test_rect=[0, 0, 300, 300],
+      revision=1),
+
+    PixelTestPage(
       'pixel_scissor.html',
       base_name + '_ScissorTestWithPreserveDrawingBuffer',
       test_rect=[0, 0, 300, 300],
       revision=0, # This is not used.
       expected_colors=[
         {
           'comment': 'red top',
           'location': [1, 1],
           'size': [198, 188],
           'color': [255, 0, 0],
@@ skipping 394 matching lines @@
       revision=1,
       browser_args=browser_args),
 
     PixelTestPage(
       'pixel_video_vp9.html',
       base_name + '_DirectComposition_Video_VP9',
       test_rect=[0, 0, 300, 300],
       revision=1,
       browser_args=browser_args),
   ]