Add MemoryPurgeController

Source/core/layout/LayoutView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 57 matching lines @@
 {
     // init LayoutObject attributes
     setInline(false);
 
     m_minPreferredLogicalWidth = 0;
     m_maxPreferredLogicalWidth = 0;
 
     setPreferredLogicalWidthsDirty(MarkOnlyThis);
 
     setPositionState(AbsolutePosition); // to 0,0 :)
+
+    if (document->page())
+        document->page()->memoryPurgeController().addListener(this);
 }
 
 LayoutView::~LayoutView()
 {
+    if (document().page())
+        document().page()->memoryPurgeController().removeListener(this);
 }
 
 bool LayoutView::hitTest(HitTestResult& result)
 {
     // We have to recursively update layout/style here because otherwise, when the hit test recurses
     // into a child document, it could trigger a layout on the parent document, which can destroy DeprecatedPaintLayer
     // that are higher up in the call stack, leading to crashes.
     // Note that Document::updateLayout calls its parent's updateLayout.
     frameView()->updateLifecycleToCompositingCleanPlusScrolling();
     return hitTestNoLifecycleUpdate(result);
@@ skipping 913 matching lines @@
     float scale = m_frameView ? m_frameView->frame().pageZoomFactor() : 1;
     return viewHeight(IncludeScrollbars) / scale;
 }
 
 void LayoutView::willBeDestroyed()
 {
     LayoutBlockFlow::willBeDestroyed();
     m_compositor.clear();
 }
 
+// TODO(bashi): Remove
+void LayoutView::purgeMemory(MemoryPurgeMode, DeviceKind)
+{
+    m_hitTestCache.clear();
+}
+
 } // namespace blink