cc: Make custom scrollbar scroll on main thread

third_party/WebKit/Source/web/tests/ScrollingCoordinatorTest.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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 #include "core/page/scrolling/ScrollingCoordinator.h"
 
+#include "core/css/CSSStyleSheet.h"
+#include "core/css/StyleSheetList.h"
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/api/LayoutViewItem.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
 #include "core/page/Page.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/testing/URLTestHelpers.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebLayer.h"
@@ skipping 591 matching lines @@
     EXPECT_TRUE(static_cast<LayoutBoxModelObject*>(fixedPos->layoutObject())->layer()->hasCompositedLayerMapping());
     EXPECT_FALSE(scrollLayer->shouldScrollOnMainThread());
 
     fixedPos->setInlineStyleProperty(CSSPropertyTransform, CSSValueNone);
     forceFullCompositingUpdate();
 
     EXPECT_FALSE(static_cast<LayoutBoxModelObject*>(fixedPos->layoutObject())->layer()->hasCompositedLayerMapping());
     EXPECT_TRUE(scrollLayer->shouldScrollOnMainThread());
 }
 
+TEST_F(ScrollingCoordinatorTest, CustomScrollbarShouldTriggerMainThreadScroll)
+{
+    webViewImpl()->settings()->setPreferCompositingToLCDTextEnabled(true);
+    webViewImpl()->setDeviceScaleFactor(2.f);
+    registerMockedHttpURLLoad("custom_scrollbar.html");
+    navigateTo(m_baseURL + "custom_scrollbar.html");
+    forceFullCompositingUpdate();
+
+    Document* document = frame()->document();
+    Element* container = document->getElementById("container");
+    Element* content = document->getElementById("content");
+    DCHECK_EQ(container->getAttribute(HTMLNames::classAttr), "custom_scrollbar");
+    DCHECK(container);
+    DCHECK(content);
+
+    LayoutObject* layoutObject = container->layoutObject();
+    ASSERT_TRUE(layoutObject->isBox());
+    LayoutBox* box = toLayoutBox(layoutObject);
+    ASSERT_TRUE(box->usesCompositedScrolling());
+    CompositedLayerMapping* compositedLayerMapping = box->layer()->compositedLayerMapping();
+    GraphicsLayer* scrollbarGraphicsLayer = compositedLayerMapping->layerForVerticalScrollbar();
+    ASSERT_TRUE(scrollbarGraphicsLayer);
+    ASSERT_TRUE(scrollbarGraphicsLayer->platformLayer()->shouldScrollOnMainThread());
+    ASSERT_TRUE(scrollbarGraphicsLayer->platformLayer()->mainThreadScrollingReasons() & MainThreadScrollingReason::kCustomScrollbarScrolling);
+
+    // remove custom scrollbar class, the scrollbar is expected to scroll on
+    // impl thread as it is an overlay scrollbar.
+    container->removeAttribute("class");
+    forceFullCompositingUpdate();
+    scrollbarGraphicsLayer = compositedLayerMapping->layerForVerticalScrollbar();
+    ASSERT_FALSE(scrollbarGraphicsLayer->platformLayer()->shouldScrollOnMainThread());
+    ASSERT_FALSE(scrollbarGraphicsLayer->platformLayer()->mainThreadScrollingReasons() & MainThreadScrollingReason::kCustomScrollbarScrolling);
+}
+
 } // namespace blink