Oilpan: move 2D Canvas and WebGL objects to the heap.

Source/bindings/core/v8/Nullable.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef Nullable_h
 #define Nullable_h
 
+#include "platform/heap/Handle.h"
 #include "wtf/Assertions.h"
 
 namespace WebCore {
 
 template <typename T>
 class Nullable {
+    DISALLOW_ALLOCATION();
 public:
     Nullable()
         : m_value()
         , m_isNull(true) { }
 
     Nullable(const T& value)
         : m_value(value)
         , m_isNull(false) { }
 
     Nullable(const Nullable& other)
@@ skipping 10 matching lines @@
     T get() const { ASSERT(!m_isNull); return m_value; }
     bool isNull() const { return m_isNull; }
 
     operator bool() const { return !m_isNull && m_value; }
 
     bool operator==(const Nullable& other) const
     {
         return (m_isNull && other.m_isNull) || (!m_isNull && !other.m_isNull && m_value == other.m_value);
     }
 
+    void trace(Visitor*)
+    {
+        // FIXME: candidate for EnableIf<> and NeedsTracing<>, somehow ?

[sof, 2014/07/12 07:22:09]

When rebasing past r177935's addition of Nullable<> as a return type for
getAttachedShaders(), I noticed that Nullable doesn't handle traceable values.

We need to include a trace() method depending on the nullable's type; the
workaround here just provides it always (and doesn't do much tracing, just
keeping the GC plugin checks quiet.)

I also annotated the class with DISALLOW_ALLOCATION().

+        (void)m_value;
+    }
+
 private:
     T m_value;
     bool m_isNull;
 };
 
 } // namespace WebCore
 
 #endif // Nullable_h