Blink side of changes to enable cache clearing without a flag.

Source/platform/graphics/ContentLayerDelegate.cpp

 /*
  * Copyright (C) 2012 Google 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 54 matching lines @@
         context.setAnnotationMode(AnnotateAll);
 
     m_painter->paint(context, clip);
 
     if (DisplayItemList* displayItemList = m_painter->displayItemList())
         displayItemList->endNewPaints();
 }
 
 void ContentLayerDelegate::paintContents(
     WebDisplayItemList* webDisplayItemList, const WebRect& clip,
-    WebContentLayerClient::GraphicsContextStatus contextStatus)
+    const bool clearCaches, WebContentLayerClient::GraphicsContextStatus contextStatus)
 {
     // Once Slimming Paint is fully implemented, this method will no longer
     // be needed since Blink will be in charge of creating the display list
     // during the document lifecylcle.
 
+    if (clearCaches)
+        m_painter->displayItemList()->invalidateAll();
+
     // Some layers don't yet produce display lists. To handle such layers, we
     // create a canvas backed by an SkPicture, and manually insert this
     // SkPicture into the WebDisplayItemList when the layer's display list is
     // empty.
     SkPictureRecorder recorder;
     RefPtr<SkPicture> picture;
     SkCanvas* canvas = recorder.beginRecording(clip.width, clip.height);
     canvas->save();
     canvas->translate(-clip.x, -clip.y);
     canvas->clipRect(SkRect::MakeXYWH(clip.x, clip.y, clip.width, clip.height));
     paintContents(canvas, clip, contextStatus);
     canvas->restore();
     picture = adoptRef(recorder.endRecording());
 
     const PaintList& paintList = m_painter->displayItemList()->paintList();
     for (PaintList::const_iterator it = paintList.begin(); it != paintList.end(); ++it)
         (*it)->appendToWebDisplayItemList(webDisplayItemList);
 }
 
 } // namespace blink