Only composite opacity animations when already in compositing mode

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1659 matching lines @@
 
 bool RenderLayerCompositor::requiresCompositingForBackfaceVisibilityHidden(RenderObject* renderer) const
 {
     return canRender3DTransforms() && renderer->style()->backfaceVisibility() == BackfaceVisibilityHidden;
 }
 
 bool RenderLayerCompositor::requiresCompositingForAnimation(RenderObject* renderer) const
 {
     if (!(m_compositingTriggers & ChromeClient::AnimationTrigger))
         return false;
-    return renderer->animation().isRunningAcceleratableAnimationOnRenderer(renderer);
+
+    // FIXME: Remove this condition once force-compositing-mode is enabled on all platforms.
+    bool shouldAccelerateOpacity = inCompositingMode();
+    return renderer->animation().isRunningAcceleratableAnimationOnRenderer(renderer, shouldAccelerateOpacity);
 }
 
 bool RenderLayerCompositor::requiresCompositingForTransition(RenderObject* renderer) const
 {
     if (!(m_compositingTriggers & ChromeClient::AnimationTrigger))
         return false;
 
     if (Settings* settings = m_renderView->document().settings()) {
         if (!settings->acceleratedCompositingForTransitionEnabled())
             return false;
@@ skipping 753 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore