Disable scrollbars on the root scroller when using visual viewport scrollbars.

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 53 matching lines @@
 #include "core/layout/LayoutTheme.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/api/LayoutBoxItem.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/FocusController.h"
 #include "core/page/Page.h"
 #include "core/page/scrolling/RootScrollerController.h"
+#include "core/page/scrolling/RootScrollerUtil.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
+#include "core/page/scrolling/TopDocumentRootScrollerController.h"
 #include "core/paint/PaintLayerFragment.h"
 #include "platform/PlatformGestureEvent.h"
 #include "platform/PlatformMouseEvent.h"
 #include "platform/graphics/CompositorMutableProperties.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingRecorder.h"
 #include "platform/scroll/ScrollAnimatorBase.h"
 #include "platform/scroll/ScrollbarTheme.h"
 #include "public/platform/Platform.h"
 
@@ skipping 713 matching lines @@
   if (scrollOriginChanged())
     setScrollOffsetUnconditionally(clampScrollOffset(scrollOffset()));
   else
     ScrollableArea::setScrollOffset(scrollOffset(), ClampingScroll);
 
   setNeedsScrollOffsetClamp(false);
   resetScrollOriginChanged();
   m_scrollbarManager.destroyDetachedScrollbars();
 }
 
+void PaintLayerScrollableArea::didChangeGlobalRootScroller() {
+  // On Android, where the VisualViewport supplies scrollbars, we need to
+  // remove the PLSA's scrollbars. In general, this would be problematic as
+  // that can cause layout but this should only ever apply with overlay
+  // scrollbars.
+  if (!ScrollbarTheme::theme().usesOverlayScrollbars())
+    return;
+
+  bool needsHorizontalScrollbar;
+  bool needsVerticalScrollbar;
+  computeScrollbarExistence(needsHorizontalScrollbar, needsVerticalScrollbar);
+  setHasHorizontalScrollbar(needsHorizontalScrollbar);
+  setHasVerticalScrollbar(needsVerticalScrollbar);
+}
+
 bool PaintLayerScrollableArea::shouldPerformScrollAnchoring() const {
   return RuntimeEnabledFeatures::scrollAnchoringEnabled() &&
          m_scrollAnchor.hasScroller() &&
          layoutBox()->style()->overflowAnchor() != AnchorNone &&
          !box().document().finishingOrIsPrinting();
 }
 
 FloatQuad PaintLayerScrollableArea::localToVisibleContentQuad(
     const FloatQuad& quad,
     const LayoutObject* localObject,
@@ skipping 903 matching lines @@
 
 void PaintLayerScrollableArea::setTopmostScrollChild(PaintLayer* scrollChild) {
   // We only want to track the topmost scroll child for scrollable areas with
   // overlay scrollbars.
   if (!hasOverlayScrollbars())
     return;
   m_nextTopmostScrollChild = scrollChild;
 }
 
 bool PaintLayerScrollableArea::visualViewportSuppliesScrollbars() const {
-  if (!layer()->isRootLayer())
+  LocalFrame* frame = box().frame();
+  if (!frame || !frame->settings())
     return false;
 
-  LocalFrame* frame = box().frame();
-  if (!frame || !frame->isMainFrame() || !frame->settings())
+  // On desktop, we always use the layout viewport's scrollbars.
+  if (!frame->settings()->viewportEnabled())
     return false;
 
-  return frame->settings()->viewportEnabled();
+  const TopDocumentRootScrollerController& controller =
+      layoutBox()->document().frameHost()->globalRootScrollerController();

[skobes, 2016/11/15 20:18:44]

You could just do frame->host() here.

[bokan, 2016/11/15 22:04:10]

Done.

+
+  if (!controller.globalRootScroller())
+    return false;
+
+  return RootScrollerUtil::scrollableAreaFor(
+             *controller.globalRootScroller()) == this;
 }
 
 Widget* PaintLayerScrollableArea::getWidget() {
   return box().frame()->view();
 }
 
 void PaintLayerScrollableArea::resetRebuildScrollbarLayerFlags() {
   m_rebuildHorizontalScrollbarLayer = false;
   m_rebuildVerticalScrollbarLayer = false;
 }
@@ skipping 218 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetsAfterLayout();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink