Fix Compositing of Opaque Scrolling Layers and Add Tests

third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp
index f11b78585bf5bbf4aa33df3d6d844357746ec8e4..488df2e9ba631eed60fa1ea9e0e26446319a4fc5 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp
@@ -4,6 +4,8 @@
 
 #include "core/paint/PaintLayerScrollableAreaTest.h"
 
+#include "platform/graphics/GraphicsLayer.h"
+
 namespace blink {
 
 TEST_F(PaintLayerScrollableAreaTest, OpaqueLayersPromoted)
@@ -12,17 +14,20 @@ TEST_F(PaintLayerScrollableAreaTest, OpaqueLayersPromoted)
 
     setBodyInnerHTML(
         "<style>"
-        "#scroller { overflow: scroll; height: 300px; width: 300px; background-color: rgb(0,128,0); }"
-        "#scrolled { height: 1000px; width: 250px; }"
+        "#scroller { overflow: scroll; height: 200px; width: 200px; background: white local content-box; border: 10px solid rgba(0, 255, 0, 0.5); }"
+        "#scrolled { height: 300px; }"
         "</style>"
         "<div id=\"scroller\"><div id=\"scrolled\"></div></div>");
     document().view()->updateAllLifecyclePhases();
 
-    ASSERT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
+    EXPECT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
     Element* scroller = document().getElementById("scroller");
     PaintLayer* paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
     ASSERT_TRUE(paintLayer);
-    ASSERT_TRUE(paintLayer->needsCompositedScrolling());
+    EXPECT_TRUE(paintLayer->needsCompositedScrolling());
+    EXPECT_TRUE(paintLayer->graphicsLayerBacking());
+    ASSERT_TRUE(paintLayer->graphicsLayerBackingForScrolling());
+    EXPECT_TRUE(paintLayer->graphicsLayerBackingForScrolling()->contentsOpaque());
 }
 
 TEST_F(PaintLayerScrollableAreaTest, TransparentLayersNotPromoted)
@@ -31,17 +36,77 @@ TEST_F(PaintLayerScrollableAreaTest, TransparentLayersNotPromoted)
 
     setBodyInnerHTML(
         "<style>"
-        "#scroller { overflow: scroll; height: 300px; width: 300px; background-color: rgba(0,128,0,0.5); }"
-        "#scrolled { height: 1000px; width: 250px; }"
+        "#scroller { overflow: scroll; height: 200px; width: 200px; background: rgba(0, 255, 0, 0.5) local content-box; border: 10px solid rgba(0, 255, 0, 0.5); }"
+        "#scrolled { height: 300px; }"
+        "</style>"
+        "<div id=\"scroller\"><div id=\"scrolled\"></div></div>");
+    document().view()->updateAllLifecyclePhases();
+
+    EXPECT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
+    Element* scroller = document().getElementById("scroller");
+    PaintLayer* paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
+    ASSERT_TRUE(paintLayer);
+    EXPECT_TRUE(!paintLayer->needsCompositedScrolling());
+    EXPECT_TRUE(!paintLayer->graphicsLayerBacking());
+    EXPECT_TRUE(!paintLayer->graphicsLayerBackingForScrolling());
+}
+
+TEST_F(PaintLayerScrollableAreaTest, OpaqueLayersDepromotedOnStyleChange)
+{
+    RuntimeEnabledFeatures::setCompositeOpaqueScrollersEnabled(true);
+
+    setBodyInnerHTML(
+        "<style>"
+        "#scroller { overflow: scroll; height: 200px; width: 200px; background: white local content-box; border: 10px solid rgba(0, 255, 0, 0.5); }"
+        "#scrolled { height: 300px; }"
+        "</style>"
+        "<div id=\"scroller\"><div id=\"scrolled\"></div></div>");
+    document().view()->updateAllLifecyclePhases();
+
+    EXPECT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
+    Element* scroller = document().getElementById("scroller");
+    PaintLayer* paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
+    ASSERT_TRUE(paintLayer);
+    EXPECT_TRUE(paintLayer->needsCompositedScrolling());
+
+    // Change the background to transparent
+    scroller->setAttribute(HTMLNames::styleAttr, "background: rgba(255,255,255,0.5) local content-box;");
+    document().view()->updateAllLifecyclePhases();
+    paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
+    ASSERT_TRUE(paintLayer);
+    EXPECT_TRUE(!paintLayer->needsCompositedScrolling());
+    EXPECT_TRUE(!paintLayer->graphicsLayerBacking());
+    EXPECT_TRUE(!paintLayer->graphicsLayerBackingForScrolling());
+}
+
+TEST_F(PaintLayerScrollableAreaTest, OpaqueLayersPromotedOnStyleChange)
+{
+    RuntimeEnabledFeatures::setCompositeOpaqueScrollersEnabled(true);
+
+    setBodyInnerHTML(
+        "<style>"
+        "#scroller { overflow: scroll; height: 200px; width: 200px; background: rgba(255,255,255,0.5) local content-box; border: 10px solid rgba(0, 255, 0, 0.5); }"
+        "#scrolled { height: 300px; }"
         "</style>"
         "<div id=\"scroller\"><div id=\"scrolled\"></div></div>");
     document().view()->updateAllLifecyclePhases();
 
-    ASSERT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
+    EXPECT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
     Element* scroller = document().getElementById("scroller");
     PaintLayer* paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
     ASSERT_TRUE(paintLayer);
-    ASSERT_TRUE(!paintLayer->needsCompositedScrolling());
+    EXPECT_TRUE(!paintLayer->needsCompositedScrolling());
+
+    // Change the background to transparent
+    scroller->setAttribute(HTMLNames::styleAttr, "background: white local content-box;");
+    document().view()->updateAllLifecyclePhases();
+    paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
+    ASSERT_TRUE(paintLayer);
+    EXPECT_TRUE(paintLayer->needsCompositedScrolling());
+    EXPECT_TRUE(paintLayer->graphicsLayerBacking());
+    ASSERT_TRUE(paintLayer->graphicsLayerBackingForScrolling());
+    EXPECT_TRUE(paintLayer->graphicsLayerBackingForScrolling()->contentsOpaque());
 }
 
+
 }