Make WebGL extensions get lost when context is lost.

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/canvas/WebGLRenderingContext.h"
+#include "wtf/RefCounted.h"
 
 namespace WebCore {
 
-class WebGLExtension {
+class WebGLExtension : public RefCounted<WebGLExtension> {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     // Extension names are needed to properly wrap instances in JavaScript objects.
     enum ExtensionName {
         EXTFragDepthName,
         EXTTextureFilterAnisotropicName,
         OESElementIndexUintName,
         OESStandardDerivativesName,
         OESTextureFloatLinearName,
         OESTextureFloatName,
         OESTextureHalfFloatLinearName,
         OESTextureHalfFloatName,
         OESVertexArrayObjectName,
         WebGLCompressedTextureATCName,
         WebGLCompressedTexturePVRTCName,
         WebGLCompressedTextureS3TCName,
         WebGLDebugRendererInfoName,
         WebGLDebugShadersName,
         WebGLDepthTextureName,
         WebGLDrawBuffersName,
         WebGLLoseContextName,
     };
 
-    void ref() { m_context->ref(); }
-    void deref() { m_context->deref(); }
     WebGLRenderingContext* context() { return m_context; }
 
     virtual ~WebGLExtension();
     virtual ExtensionName getName() 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 WebGLRenderingContext.
+    virtual void lose(bool)
+    {
+        m_context = 0;
+    }
+
+    bool isLost()
+    {
+        return !m_context;
+    }
+
 protected:
     WebGLExtension(WebGLRenderingContext*);
+
     WebGLRenderingContext* m_context;
 };
 
 } // namespace WebCore
 
 #endif // WebGLExtension_h