Fix the bug that negative outline-offset is covered up by composited

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp

 // Copyright 2014 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/layout/compositing/CompositedLayerMapping.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/api/LayoutViewItem.h"
@@ skipping 819 matching lines @@
   ASSERT_TRUE(mapping->scrollingContentsLayer());
   EXPECT_EQ(
       static_cast<GraphicsLayerPaintingPhase>(
           GraphicsLayerPaintOverflowContents |
           GraphicsLayerPaintCompositedScroll | GraphicsLayerPaintForeground),
       mapping->scrollingContentsLayer()->paintingPhase());
   EXPECT_FALSE(mapping->foregroundLayer());
 }
 
 TEST_P(CompositedLayerMappingTest,
+       DecorationLayerOnlyCreatedInCompositedScrolling) {
+  setBodyInnerHTML(
+      "<div id='target' style='height: 200px; "
+      "will-change: transform;'></div>");

[flackr, 2016/11/17 16:10:45]

This element should have a negative offset outline such that if it were a
composited scroller it would get a decoration layer. Perhaps the test could
actually verify that it does by switching from overflow: visible to overflow:
scroll.

[yigu, 2016/11/18 04:14:07]

Done.

+  document().view()->updateAllLifecyclePhases();
+
+  Element* element = document().getElementById("target");
+  PaintLayer* paintLayer =
+      toLayoutBoxModelObject(element->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+
+  // No decoration layer is created when not composited scrolling.
+  EXPECT_TRUE(paintLayer->hasCompositedLayerMapping());
+  EXPECT_FALSE(paintLayer->needsCompositedScrolling());
+
+  CompositedLayerMapping* mapping = paintLayer->compositedLayerMapping();
+  EXPECT_FALSE(mapping->decorationLayer());
+}
+
+TEST_P(CompositedLayerMappingTest,
+       DecorationLayerCreatedAndDestroyedInCompositedScrolling) {
+  setBodyInnerHTML(
+      "<style>"
+      "#scroller { overflow: scroll; height: 200px; width: 200px; background: "
+      "white local content-box; outline: 1px solid blue;}"
+      "#scrolled { height: 300px; }"
+      "</style>"
+      "<div id=\"parent\">"
+      "  <div id=\"scroller\"><div id=\"scrolled\"></div></div>"
+      "</div>");
+  document().view()->updateAllLifecyclePhases();
+
+  Element* scroller = document().getElementById("scroller");
+  PaintLayer* paintLayer =
+      toLayoutBoxModelObject(scroller->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+
+  CompositedLayerMapping* mapping = paintLayer->compositedLayerMapping();
+  EXPECT_FALSE(mapping->decorationLayer());
+
+  // The decoration layer is created when composited scrolling
+  // with an outline drawn over the composited scrolling region.
+  scroller->setAttribute(HTMLNames::styleAttr, "outline-offset: -2px;");
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+
+  mapping = paintLayer->compositedLayerMapping();
+  EXPECT_TRUE(paintLayer->needsCompositedScrolling());
+  EXPECT_TRUE(mapping->decorationLayer());
+
+  // The decoration layer is destroyed when the scrolling region
+  // will not be covered up by the outline.
+  scroller->removeAttribute(HTMLNames::styleAttr);
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(scroller->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+
+  mapping = paintLayer->compositedLayerMapping();
+  EXPECT_FALSE(mapping->decorationLayer());
+}
+
+TEST_P(CompositedLayerMappingTest,
        BackgroundPaintedIntoGraphicsLayerIfNotCompositedScrolling) {
   document().frame()->settings()->setPreferCompositingToLCDTextEnabled(true);
   setBodyInnerHTML(
       "<div id='container' style='overflow: scroll; width: 300px; height: "
       "300px; border-radius: 5px; background: white; will-change: transform;'>"
       "    <div style='background-color: blue; width: 2000px; height: "
       "2000px;'></div>"
       "</div>");
 
   PaintLayer* layer =
@@ skipping 151 matching lines @@
     document().view()->updateAllLifecyclePhases();
     ASSERT_EQ(document().documentElement(),
               rootScrollerController.globalRootScroller());
 
     EXPECT_TRUE(mapping3->clippingLayer());
     EXPECT_TRUE(mapping3->clippingLayer()->platformLayer()->masksToBounds());
   }
 }
 
 }  // namespace blink