Merge 185069 "Enforce context refrence guards in WebGL extensions."

Source/core/html/canvas/WebGLExtension.h

 /*
  * Copyright (C) 2010 Google 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
  *     documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (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 WebGLExtension_h
 #define WebGLExtension_h
 
+#include "core/html/HTMLCanvasElement.h"
 #include "core/html/canvas/WebGLExtensionName.h"
 #include "core/html/canvas/WebGLRenderingContextBase.h"
 #include "platform/heap/Handle.h"
 #include "wtf/RefCounted.h"
 
 namespace blink {
 
+class WebGLExtensionScopedContext : public NoBaseWillBeGarbageCollectedFinalized<WebGLExtensionScopedContext> {
+    WTF_MAKE_NONCOPYABLE(WebGLExtensionScopedContext);
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+public:
+    WebGLExtensionScopedContext(WebGLExtension*);
+    virtual ~WebGLExtensionScopedContext();
+
+    bool isLost() { return !m_context; }
+    WebGLRenderingContextBase* context() const { return m_context.get(); }
+
+    virtual void trace(Visitor*);
+
+private:
+    RefPtrWillBeMember<WebGLRenderingContextBase> m_context;
+};
+
 class WebGLExtension : public RefCountedWillBeGarbageCollectedFinalized<WebGLExtension> {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
-    WebGLRenderingContextBase* context() { return m_context; }
-
     virtual ~WebGLExtension();
     virtual WebGLExtensionName name() const = 0;
 
     // Lose this extension. Passing true = force loss. Some extensions
     // like WEBGL_lose_context are not normally lost when the context
     // is lost but must be lost when destroying their WebGLRenderingContextBase.
     virtual void lose(bool)
     {
         m_context = nullptr;
     }
 
-    bool isLost()
-    {
-        return !m_context;
-    }
+    bool isLost() { return !m_context; }
 
     virtual void trace(Visitor*);
 
 protected:
     explicit WebGLExtension(WebGLRenderingContextBase*);
 
+private:
+    friend WebGLExtensionScopedContext;
+
     RawPtrWillBeWeakMember<WebGLRenderingContextBase> m_context;
 };
 
 } // namespace blink
 
 #endif // WebGLExtension_h