Replace RenderArena with PartitionAlloc.

Source/core/rendering/RenderWidget.cpp

Index: Source/core/rendering/RenderWidget.cpp
diff --git a/Source/core/rendering/RenderWidget.cpp b/Source/core/rendering/RenderWidget.cpp
index 2d76543b739a523c3c0cdd9ba7949c036df664f9..97276523c27cd8b117603c190e67f02fc98a7d4d 100644
--- a/Source/core/rendering/RenderWidget.cpp
+++ b/Source/core/rendering/RenderWidget.cpp
@@ -31,7 +31,6 @@
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderLayerBacking.h"
 #include "core/rendering/RenderView.h"
-#include "core/rendering/RenderWidgetProtector.h"
 
 using namespace std;
 
@@ -112,11 +111,9 @@ void RenderWidget::destroy()
 {
     willBeDestroyed();
 
-    // Grab the arena from node()->document()->renderArena() before clearing the node pointer.
     // Clear the node before deref-ing, as this may be deleted when deref is called.
-    RenderArena* arena = renderArena();
     clearNode();
-    deref(arena);
+    deref();
 }
 
 RenderWidget::~RenderWidget()
@@ -148,7 +145,6 @@ bool RenderWidget::setWidgetGeometry(const LayoutRect& frame)
 
     m_clipRect = clipRect;
 
-    RenderWidgetProtector protector(this);
     RefPtr<Node> protectedNode(node());
     m_widget->setFrameRect(newFrame);
 
@@ -318,10 +314,10 @@ void RenderWidget::setOverlapTestResult(bool isOverlapped)
     toFrameView(m_widget.get())->setIsOverlapped(isOverlapped);
 }
 
-void RenderWidget::deref(RenderArena *arena)
+void RenderWidget::deref()
 {
     if (--m_refCount <= 0)
-        arenaDelete(arena, this);
+        postDestroy();
 }
 
 void RenderWidget::updateWidgetPosition()