Don't clip invalidation of composited scrolling contents

Source/core/rendering/PaintInvalidationState.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/rendering/PaintInvalidationState.h"
 
 #include "core/rendering/RenderInline.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderView.h"
@@ skipping 69 matching lines @@
 
     // FIXME: <http://bugs.webkit.org/show_bug.cgi?id=13443> Apply control clip if present.
 }
 
 void PaintInvalidationState::applyClipIfNeeded(const RenderObject& renderer)
 {
     if (!renderer.hasOverflowClip())
         return;
 
     const RenderBox& box = toRenderBox(renderer);
+    m_paintOffset -= box.scrolledContentOffset();
+
+    // Do not clip scroll layer contents because the compositor expects the whole layer
+    // to be always invalidated in-time.
+    if (box.usesCompositedScrolling()) {
+        ASSERT(!m_clipped); // The box should establish paint invalidation container, so no m_clipped inherited.
+        return;
+    }
+
     LayoutRect clipRect(toPoint(m_paintOffset), box.layer()->size());
     if (m_clipped) {
         m_clipRect.intersect(clipRect);
     } else {
         m_clipRect = clipRect;
         m_clipped = true;
     }
-    m_paintOffset -= box.scrolledContentOffset();
 }
 
 } // namespace blink