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

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 71 matching lines @@
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/loader/DocumentLoader.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/observer/ResizeObserverController.h"
 #include "core/page/AutoscrollController.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/FocusController.h"
 #include "core/page/FrameTree.h"
 #include "core/page/Page.h"
+#include "core/page/scrolling/RootScrollerUtil.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "core/page/scrolling/TopDocumentRootScrollerController.h"
 #include "core/paint/FramePainter.h"
 #include "core/paint/PaintLayer.h"
 #include "core/paint/PrePaintTreeWalk.h"
 #include "core/plugins/PluginView.h"
 #include "core/style/ComputedStyle.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "core/svg/SVGSVGElement.h"
 #include "platform/Histogram.h"
@@ skipping 2564 matching lines @@
   if (!parent())
     return nullptr;
 
   Frame* parentFrame = m_frame->tree().parent();
   if (parentFrame && parentFrame->isLocalFrame())
     return toLocalFrame(parentFrame)->view();
 
   return nullptr;
 }
 
+void FrameView::didChangeGlobalRootScroller() {
+  if (!ScrollbarTheme::theme().usesOverlayScrollbars())
+    return;
+
+  // Avoid drawing two sets of scrollbars when visual viewport is enabled.
+  bool shouldHaveHorizontalScrollbar = false;
+  bool shouldHaveVerticalScrollbar = false;
+  computeScrollbarExistence(shouldHaveHorizontalScrollbar,
+                            shouldHaveVerticalScrollbar, contentsSize());
+  m_scrollbarManager.setHasHorizontalScrollbar(shouldHaveHorizontalScrollbar);
+  m_scrollbarManager.setHasVerticalScrollbar(shouldHaveVerticalScrollbar);
+}
+
 void FrameView::updateWidgetGeometriesIfNeeded() {
   if (!m_needsUpdateWidgetGeometries)
     return;
 
   m_needsUpdateWidgetGeometries = false;
 
   updateWidgetGeometries();
 }
 
 void FrameView::updateAllLifecyclePhases() {
@@ skipping 804 matching lines @@
 void FrameView::removeChild(Widget* child) {
   ASSERT(child->parent() == this);
 
   if (child->isFrameView())
     removeScrollableArea(toFrameView(child));
 
   child->setParent(0);
   m_children.remove(child);
 }
 
-bool FrameView::visualViewportSuppliesScrollbars() const {
-  return m_frame->isMainFrame() && m_frame->settings() &&
-         m_frame->settings()->viewportEnabled();
+bool FrameView::visualViewportSuppliesScrollbars() {
+  // On desktop, we always use the layout viewport's scrollbars.
+  if (!m_frame->settings() || !m_frame->settings()->viewportEnabled() ||
+      !m_frame->document() || !m_frame->document()->frameHost())
+    return false;
+
+  const TopDocumentRootScrollerController& controller =
+      m_frame->document()->frameHost()->globalRootScrollerController();
+
+  if (!controller.globalRootScroller())
+    return false;
+
+  return RootScrollerUtil::scrollableAreaFor(
+             *controller.globalRootScroller()) ==
+         layoutViewportScrollableArea();
 }
 
 AXObjectCache* FrameView::axObjectCache() const {
   if (frame().document())
     return frame().document()->existingAXObjectCache();
   return nullptr;
 }
 
 void FrameView::setCursor(const Cursor& cursor) {
   Page* page = frame().page();
@@ skipping 236 matching lines @@
 bool FrameView::hasOverlayScrollbars() const {
   return (horizontalScrollbar() &&
           horizontalScrollbar()->isOverlayScrollbar()) ||
          (verticalScrollbar() && verticalScrollbar()->isOverlayScrollbar());
 }
 
 void FrameView::computeScrollbarExistence(
     bool& newHasHorizontalScrollbar,
     bool& newHasVerticalScrollbar,
     const IntSize& docSize,
-    ComputeScrollbarExistenceOption option) const {
-  if (m_frame->settings() && m_frame->settings()->hideScrollbars()) {
+    ComputeScrollbarExistenceOption option) {
+  if ((m_frame->settings() && m_frame->settings()->hideScrollbars()) ||
+      visualViewportSuppliesScrollbars()) {
     newHasHorizontalScrollbar = false;
     newHasVerticalScrollbar = false;
     return;
   }
 
   bool hasHorizontalScrollbar = horizontalScrollbar();
   bool hasVerticalScrollbar = verticalScrollbar();
 
   newHasHorizontalScrollbar = hasHorizontalScrollbar;
   newHasVerticalScrollbar = hasVerticalScrollbar;
@@ skipping 823 matching lines @@
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.width();
 }
 
 int FrameView::initialViewportHeight() const {
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.height();
 }
 
 }  // namespace blink