Keep TextMetrics on the Oilpan heap always.

Source/core/html/TextMetrics.h

 /*
  * Copyright (C) 2008 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 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef TextMetrics_h
 #define TextMetrics_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
-#include "wtf/PassRefPtr.h"
-#include "wtf/RefCounted.h"
 
 namespace blink {
 
-class CORE_EXPORT TextMetrics final : public RefCountedWillBeGarbageCollected<TextMetrics>, public ScriptWrappable {
+class CORE_EXPORT TextMetrics final : public GarbageCollected<TextMetrics>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtrWillBeRawPtr<TextMetrics> create() { return adoptRefWillBeNoop(new TextMetrics); }
+    static TextMetrics* create()
+    {
+        return new TextMetrics;
+    }
 
     float width() const { return m_width; }
     void setWidth(float w) { m_width = w; }
 
     float actualBoundingBoxLeft() const { return m_actualBoundingBoxLeft; }
     void setActualBoundingBoxLeft(float actualBoundingBoxLeft) { m_actualBoundingBoxLeft = actualBoundingBoxLeft; }
 
     float actualBoundingBoxRight() const { return m_actualBoundingBoxRight; }
     void setActualBoundingBoxRight(float actualBoundingBoxRight) { m_actualBoundingBoxRight = actualBoundingBoxRight; }
 
@@ skipping 54 matching lines @@
     float m_emHeightAscent;
     float m_emHeightDescent;
     float m_hangingBaseline;
     float m_alphabeticBaseline;
     float m_ideographicBaseline;
 };
 
 } // namespace blink
 
 #endif // TextMetrics_h