Re-land "Drop background color optimization for composited layers"

Source/web/tests/GraphicsLayerTest.cpp

Index: Source/web/tests/GraphicsLayerTest.cpp
diff --git a/Source/web/tests/GraphicsLayerTest.cpp b/Source/web/tests/GraphicsLayerTest.cpp
index 0550c62e57dea8c063feb06b6d8f0536e1fae86f..fff5d6d3b92f83ebfa1f98c552a08ee132180bc2 100644
--- a/Source/web/tests/GraphicsLayerTest.cpp
+++ b/Source/web/tests/GraphicsLayerTest.cpp
@@ -165,16 +165,4 @@ TEST_F(GraphicsLayerTest, applyScrollToScrollableArea)
     EXPECT_EQ(scrollPosition, WebPoint(scrollableArea.scrollPosition()));
 }
 
-TEST_F(GraphicsLayerTest, DISABLED_setContentsToSolidColor)
-{
-    m_graphicsLayer->setContentsToSolidColor(Color::transparent);
-    EXPECT_FALSE(m_graphicsLayer->contentsLayer());
-
-    m_graphicsLayer->setContentsToSolidColor(Color::white);
-    EXPECT_TRUE(m_graphicsLayer->contentsLayer());
-
-    m_graphicsLayer->setContentsToSolidColor(Color());
-    EXPECT_FALSE(m_graphicsLayer->contentsLayer());
-}
-
 } // namespace