Fix partial painting with render pipeline throttling

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 3700 matching lines @@
     return ScrollBehaviorInstant;
 }
 
 void FrameView::paint(GraphicsContext& context, const CullRect& cullRect) const
 {
     paint(context, GlobalPaintNormalPhase, cullRect);
 }
 
 void FrameView::paint(GraphicsContext& context, const GlobalPaintFlags globalPaintFlags, const CullRect& cullRect) const
 {
-    // TODO(skyostil): Remove this early-out in favor of painting cached scrollbars.
-    if (shouldThrottleRendering())
-        return;
     FramePainter(*this).paint(context, globalPaintFlags, cullRect);
 }
 
 void FrameView::paintContents(GraphicsContext& context, const GlobalPaintFlags globalPaintFlags, const IntRect& damageRect) const
 {
-    if (shouldThrottleRendering())
-        return;
     FramePainter(*this).paintContents(context, globalPaintFlags, damageRect);
 }
 
 bool FrameView::isPointInScrollbarCorner(const IntPoint& pointInRootFrame)
 {
     if (!scrollbarCornerPresent())
         return false;
 
     IntPoint framePoint = convertFromRootFrame(pointInRootFrame);
 
@@ skipping 275 matching lines @@
     const SecurityOrigin* origin = frame().securityContext()->securityOrigin();
     for (Frame* parentFrame = m_frame->tree().parent(); parentFrame; parentFrame = parentFrame->tree().parent()) {
         const SecurityOrigin* parentOrigin = parentFrame->securityContext()->securityOrigin();
         if (!origin->canAccess(parentOrigin)) {
             m_crossOriginForThrottling = true;
             break;
         }
     }
 
     bool becameUnthrottled = wasThrottled && !canThrottleRendering();
-    if (becameUnthrottled)
+    if (becameUnthrottled) {
+        // Start ticking animation frames again if necessary.
         page()->animator().scheduleVisualUpdate(m_frame.get());
+        // Force a full repaint of this frame to ensure we are not left with a
+        // partially painted version of this frame's contents if we skipped
+        // painting them while the frame was throttled.
+        if (LayoutView* layoutView = this->layoutView())
+            layoutView->setShouldDoFullPaintInvalidation(PaintInvalidationBecameVisible);
+    }
 }
 
 bool FrameView::shouldThrottleRendering() const
 {
     return canThrottleRendering() && lifecycle().throttlingAllowed();
 }
 
 bool FrameView::canThrottleRendering() const
 {
     if (!RuntimeEnabledFeatures::renderingPipelineThrottlingEnabled())
         return false;
     return m_hiddenForThrottling && m_crossOriginForThrottling;
 }
 
 LayoutBox& FrameView::boxForScrollControlPaintInvalidation() const
 {
     ASSERT(layoutView());
     return *layoutView();
 }
 
 } // namespace blink