[devtools] Add a command to emulate the default background color.

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 178 matching lines @@
       m_subtreeThrottled(false),
       m_lifecycleUpdatesThrottled(false),
       m_needsPaintPropertyUpdate(true),
       m_currentUpdateLifecyclePhasesTargetState(
           DocumentLifecycle::Uninitialized),
       m_scrollAnchor(this),
       m_scrollbarManager(*this),
       m_needsScrollbarsUpdate(false),
       m_suppressAdjustViewSize(false),
       m_allowsLayoutInvalidationAfterLayoutClean(true),
+      m_needsOpaquenessUpdate(false),
       m_mainThreadScrollingReasons(0),
       m_mainThreadScrollingReasonsCounter(
           MainThreadScrollingReason::kMainThreadScrollingReasonCount,
           0) {
   init();
 }
 
 FrameView* FrameView::create(LocalFrame& frame) {
   FrameView* view = new FrameView(frame);
   view->show();
@@ skipping 2092 matching lines @@
 bool FrameView::hasOpaqueBackground() const {
   return !m_isTransparent && !m_baseBackgroundColor.hasAlpha();
 }
 
 Color FrameView::baseBackgroundColor() const {
   return m_baseBackgroundColor;
 }
 
 void FrameView::setBaseBackgroundColor(const Color& backgroundColor) {
   m_baseBackgroundColor = backgroundColor;
+  m_needsOpaquenessUpdate = true;
+  recalculateScrollbarOverlayColorTheme(documentBackgroundColor());
+
+  if (!shouldThrottleRendering())
+    page()->animator().scheduleVisualUpdate(m_frame.get());
+}
+
+void FrameView::updateOpaquenessIfNeeded() {
+  if (!m_needsOpaquenessUpdate)
+    return;
 
   if (!layoutViewItem().isNull() &&
       layoutViewItem().layer()->hasCompositedLayerMapping()) {
     CompositedLayerMapping* compositedLayerMapping =
         layoutViewItem().layer()->compositedLayerMapping();
     compositedLayerMapping->updateContentsOpaque();
     if (compositedLayerMapping->mainGraphicsLayer())
       compositedLayerMapping->mainGraphicsLayer()->setNeedsDisplay();
   }
-  recalculateScrollbarOverlayColorTheme(documentBackgroundColor());
-
-  if (!shouldThrottleRendering())
-    page()->animator().scheduleVisualUpdate(m_frame.get());
+  m_needsOpaquenessUpdate = false;
 }
 
 void FrameView::updateBackgroundRecursively(const Color& backgroundColor,
                                             bool transparent) {
   forAllNonThrottledFrameViews(
       [backgroundColor, transparent](FrameView& frameView) {
         frameView.setTransparent(transparent);
         frameView.setBaseBackgroundColor(backgroundColor);
       });
 }
@@ skipping 616 matching lines @@
 
       if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
         view.compositor()->updateIfNeededRecursive();
       } else {
         forAllNonThrottledFrameViews([](FrameView& frameView) {
           frameView.layoutView()->layer()->updateDescendantDependentFlags();
           frameView.layoutView()->commitPendingSelection();
         });
       }
 
+      updateOpaquenessIfNeeded();
+
       scrollContentsIfNeededRecursive();
       DCHECK(RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() ||
              lifecycle().state() >= DocumentLifecycle::CompositingClean);
 
       m_frame->host()->globalRootScrollerController().didUpdateCompositing();
 
       if (targetState >= DocumentLifecycle::PrePaintClean) {
         if (!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled())
           invalidateTreeIfNeededRecursive();
 
@@ skipping 2091 matching lines @@
     std::unique_ptr<CompositorAnimationTimeline> timeline) {
   m_animationTimeline = std::move(timeline);
 }
 
 void FrameView::setAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   m_animationHost = std::move(host);
 }
 
 }  // namespace blink