Add MemoryPurgeController

Source/core/layout/LayoutView.cpp

Index: Source/core/layout/LayoutView.cpp
diff --git a/Source/core/layout/LayoutView.cpp b/Source/core/layout/LayoutView.cpp
index 6a6419d91d6bbfc57de34fdf7748911a7464bc4a..d539a246990f2e71852302c2e000900088fac610 100644
--- a/Source/core/layout/LayoutView.cpp
+++ b/Source/core/layout/LayoutView.cpp
@@ -75,10 +75,15 @@ LayoutView::LayoutView(Document* document)
     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)
@@ -1012,4 +1017,10 @@ void LayoutView::willBeDestroyed()
     m_compositor.clear();
 }
 
+// TODO(bashi): Remove
+void LayoutView::purgeMemory(MemoryPurgeMode, DeviceKind)
+{
+    m_hitTestCache.clear();
+}
+
 } // namespace blink