Prevent implicit framebuffer clear from clobbering alpha in emulated RGB

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,
                expected_colors=None, tolerance=2, browser_args=None):
@@ skipping 273 matching lines @@
       base_name + '_WebGLGreenTriangle_NonChromiumImage_AA_NoAlpha',
       test_rect=[0, 0, 300, 300],
       revision=1,
       browser_args=non_chromium_image_args),
     PixelTestPage(
       'pixel_webgl_noaa_noalpha.html',
       base_name + '_WebGLGreenTriangle_NonChromiumImage_NoAA_NoAlpha',
       test_rect=[0, 0, 300, 300],
       revision=1,
       browser_args=non_chromium_image_args),
+    PixelTestPage(
+      'pixel_webgl_noalpha_implicit_clear.html',
+      base_name + '_WebGLGreenTriangle_NonChromiumImage_ImplicitClear',
+      test_rect=[0, 0, 300, 300],
+      revision=1,
+      browser_args=non_chromium_image_args),

[Ken Russell (switch to Gerrit), 2016/12/01 07:20:43]

Please add the new page to the set of DefaultPages, above, instead of the
MacSpecificPages. (Running with non_chromium_image_args defeats the purpose of
this test, btw.) There's a chance this test might catch a regression on another
platform before it happens. I suggest a name like
WebGLTransparentGreenTriangle_NoAlpha_ImplicitClear.

[Kai Ninomiya, 2016/12/01 23:30:19]

Done.

 
     # On macOS, test CSS filter effects with and without the CA compositor.
     PixelTestPage(
       'filter_effects.html',
       base_name + '_CSSFilterEffects',
       test_rect=[0, 0, 300, 300],
       revision=3),
     PixelTestPage(
       'filter_effects.html',
       base_name + '_CSSFilterEffects_NoOverlays',
       test_rect=[0, 0, 300, 300],
       revision=3,
       tolerance=10,
       browser_args=['--disable-mac-overlays']),
   ]