Fix Compositing of Opaque Scrolling Layers and Add Tests

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

 // 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.
 
 #include "core/paint/PaintLayerScrollableAreaTest.h"
 
+#include "platform/graphics/GraphicsLayer.h"
+
 namespace blink {
 
 TEST_F(PaintLayerScrollableAreaTest, OpaqueLayersPromoted)
 {
     RuntimeEnabledFeatures::setCompositeOpaqueScrollersEnabled(true);
 
     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)
 {
     RuntimeEnabledFeatures::setCompositeOpaqueScrollersEnabled(true);
 
     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();
 
-    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());
+    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();
+
+    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: 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());
+}
+
+
+}