Reland of place pinch scrollbars with regular scrollbars.

Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 2011 Apple 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
@@ skipping 363 matching lines @@
             if (settings->useSolidColorScrollbars()) {
                 ASSERT(RuntimeEnabledFeatures::overlayScrollbarsEnabled());
                 webScrollbarLayer = createSolidColorScrollbarLayer(orientation, scrollbar->theme()->thumbThickness(scrollbar), scrollbar->theme()->trackPosition(scrollbar), scrollableArea->shouldPlaceVerticalScrollbarOnLeft());
             } else {
                 webScrollbarLayer = createScrollbarLayer(scrollbar);
             }
             scrollbarLayer = addWebScrollbarLayer(scrollableArea, orientation, webScrollbarLayer.release());
         }
 
         WebLayer* scrollLayer = toWebLayer(scrollableArea->layerForScrolling());
-        WebLayer* containerLayer = toWebLayer(scrollableArea->layerForContainer());
-        setupScrollbarLayer(scrollbarGraphicsLayer, scrollbarLayer, scrollLayer, containerLayer);
+        WebLayer* scrollbarContainerLayer = toWebLayer(scrollableArea->layerForScrollbarContainer());
+        setupScrollbarLayer(scrollbarGraphicsLayer, scrollbarLayer, scrollLayer, scrollbarContainerLayer);
 
         // Root layer non-overlay scrollbars should be marked opaque to disable
         // blending.
         bool isOpaqueScrollbar = !scrollbar->isOverlayScrollbar();
         scrollbarGraphicsLayer->setContentsOpaque(isMainFrame && isOpaqueScrollbar);
     } else
         removeWebScrollbarLayer(scrollableArea, orientation);
 }
 
 bool ScrollingCoordinator::scrollableAreaScrollLayerDidChange(ScrollableArea* scrollableArea)
 {
     GraphicsLayer* scrollLayer = scrollableArea->layerForScrolling();
 
     if (scrollLayer) {
         ASSERT(m_page);
         scrollLayer->setScrollableArea(scrollableArea, isForViewport(scrollableArea));
     }
 
     WebLayer* webLayer = toWebLayer(scrollableArea->layerForScrolling());
     WebLayer* containerLayer = toWebLayer(scrollableArea->layerForContainer());
+    WebLayer* scrollbarContainerLayer = toWebLayer(scrollableArea->layerForScrollbarContainer());
     if (webLayer) {
         webLayer->setScrollClipLayer(containerLayer);
         // Non-layered Viewport constrained objects, e.g. fixed position elements, are
         // positioned in Blink using integer coordinates. In that case, we don't want
         // to set the WebLayer's scroll position at fractional precision otherwise the
         // WebLayer's position after snapping to device pixel can be off with regard to
         // fixed position elements.
         if (m_lastMainThreadScrollingReasons & ScrollingCoordinator::HasNonLayerViewportConstrainedObjects) {
             webLayer->setScrollPositionDouble(DoublePoint(scrollableArea->scrollPosition() - scrollableArea->minimumScrollPosition()));
         } else {
             DoublePoint scrollPosition(scrollableArea->scrollPositionDouble() - scrollableArea->minimumScrollPositionDouble());
             IntPoint flooredScrollPosition(flooredIntPoint(scrollPosition));
             DoublePoint fractionalPart(scrollPosition.x() - flooredScrollPosition.x(), scrollPosition.y() - flooredScrollPosition.y());
             webLayer->setScrollPositionDouble(scrollPosition);
             // Blink can only use the integer part of the scroll offset to position elements.
             // Sends the fractional part of the scroll offset to CC as scroll adjustment for
             // fixed-position layer.
             webLayer->setScrollCompensationAdjustment(fractionalPart);
         }
 
         webLayer->setBounds(scrollableArea->contentsSize());
         bool canScrollX = scrollableArea->userInputScrollable(HorizontalScrollbar);
         bool canScrollY = scrollableArea->userInputScrollable(VerticalScrollbar);
         webLayer->setUserScrollable(canScrollX, canScrollY);
     }
     if (WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, HorizontalScrollbar)) {
         GraphicsLayer* horizontalScrollbarLayer = scrollableArea->layerForHorizontalScrollbar();
         if (horizontalScrollbarLayer)
-            setupScrollbarLayer(horizontalScrollbarLayer, scrollbarLayer, webLayer, containerLayer);
+            setupScrollbarLayer(horizontalScrollbarLayer, scrollbarLayer, webLayer, scrollbarContainerLayer);
     }
     if (WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, VerticalScrollbar)) {
         GraphicsLayer* verticalScrollbarLayer = scrollableArea->layerForVerticalScrollbar();
+
         if (verticalScrollbarLayer)
-            setupScrollbarLayer(verticalScrollbarLayer, scrollbarLayer, webLayer, containerLayer);
+            setupScrollbarLayer(verticalScrollbarLayer, scrollbarLayer, webLayer, scrollbarContainerLayer);
     }
 
     // Update the viewport layer registration if the outer viewport may have changed.
     if (m_page->settings().rootLayerScrolls() && isForRootLayer(scrollableArea))
         m_page->chromeClient().registerViewportLayers();
 
     scrollableArea->layerForScrollingDidChange(m_programmaticScrollAnimatorTimeline.get());
 
     return !!webLayer;
 }
@@ skipping 626 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : nullptr)
         return WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace blink