Add pixel test for solid color backgrounds.

content/test/gpu/page_sets/gpu_rasterization_tests.py

Index: content/test/gpu/page_sets/gpu_rasterization_tests.py
diff --git a/content/test/gpu/page_sets/gpu_rasterization_tests.py b/content/test/gpu/page_sets/gpu_rasterization_tests.py
index d51547f765fa4632845dbef57735a4049ff7843f..444a82d93ca992126f14a483fc66d0e0497c0b25 100644
--- a/content/test/gpu/page_sets/gpu_rasterization_tests.py
+++ b/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]},