Add pixel test for solid color backgrounds.

This catches issues with compositing solid color quads.
Test is initially expected to fail until reference images are generated.

R=kbr@chromium.org
BUG=624256
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel;tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2112603003
Cr-Commit-Position: refs/heads/master@{#403193}

content/test/data/gpu/pixel_background.html

@@ -6,7 +6,7 @@
 body {
   margin: 0px;
   padding: 0px;
-  background-color: white;
+  background-color: green;
 }
 #container {
   position: relative;

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -23,3 +23,8 @@ class PixelExpectations(GpuTestExpectations):
     # TODO(ccameron): Remove suppression after rebaseline.
     self.Fail('Pixel.CSS3DBlueBox', ['mac'], bug=533690)
     self.Fail('Pixel.CSS3DBlueBoxES3', ['mac'], bug=533690)
+
+    # TODO(vmiura): Re-enable these after reference images are generated.
+    self.Fail('Pixel.SolidColorBackground', bug=624256)
+    self.Fail('Pixel.SolidColorBackgroundES3', bug=624256)
+    self.Fail('Pixel.2DCanvasWebGLES3', bug=624256)

content/test/gpu/page_sets/gpu_rasterization_tests.py

@@ -16,22 +16,22 @@ class GpuRasterizationBlueBoxPage(gpu_test_base.PageBase):
 
     self.expectations = [
       {'comment': 'body-t',
-       'color': [255, 255, 255],
+       'color': [0, 128, 0],
        'tolerance': 0,
        'location': [5, 5],
        'size': [1, 1]},
       {'comment': 'body-r',
-       'color': [255, 255, 255],
+       'color': [0, 128, 0],
        'tolerance': 0,
        'location': [215, 5],
        'size': [1, 1]},
       {'comment': 'body-b',
-       'color': [255, 255, 255],
+       'color': [0, 128, 0],
        'tolerance': 0,
        'location': [215, 215],
        'size': [1, 1]},
       {'comment': 'body-l',
-       'color': [255, 255, 255],
+       'color': [0, 128, 0],
        'tolerance': 0,
        'location': [5, 215],
        'size': [1, 1]},

content/test/gpu/page_sets/pixel_tests.py

@@ -199,13 +199,22 @@ class PixelTestsStorySet(story_set_module.StorySet):
 
     self.AddStory(PixelTestsPage(
       url='file://../../data/gpu/pixel_canvas2d_webgl.html',
-      name=base_name + '.2DCanvasWebGL',
+      name=base_name + '.2DCanvasWebGL' + es3_suffix,
       test_rect=[0, 0, 300, 300],
       revision=2,
       story_set=self,
       shared_page_state_class=shared_page_state_class,
       expectations=expectations))
 
+    self.AddStory(PixelTestsPage(
+      url='file://../../data/gpu/pixel_background.html',
+      name=base_name + '.SolidColorBackground' + es3_suffix,
+      test_rect=[500, 500, 100, 100],
+      revision=1,
+      story_set=self,
+      shared_page_state_class=shared_page_state_class,
+      expectations=expectations))
+
   @property
   def allow_mixed_story_states(self):
     # Return True here in order to be able to add the same tests with