Fix WebGL context restoration logic. The retry mechanism was broken when the ownership of the WebGr…

Source/platform/graphics/gpu/Extensions3DUtil.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 Extensions3DUtil_h
 #define Extensions3DUtil_h
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/GraphicsTypes3D.h"
 #include "third_party/khronos/GLES2/gl2.h"
 #include "third_party/khronos/GLES2/gl2ext.h"
 #include "wtf/HashSet.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 class WebGraphicsContext3D;
 }
 
 namespace WebCore {
 
 class PLATFORM_EXPORT Extensions3DUtil {
 public:
-    Extensions3DUtil(blink::WebGraphicsContext3D*);
+    // Creates a new Extensions3DUtil. If the passed WebGraphicsContext3D has been spontaneously lost, returns null.
+    static PassOwnPtr<Extensions3DUtil> create(blink::WebGraphicsContext3D*);
     ~Extensions3DUtil();
 
     bool supportsExtension(const String& name);
     bool ensureExtensionEnabled(const String& name);
     bool isExtensionEnabled(const String& name);
 
     static bool canUseCopyTextureCHROMIUM(GLenum destFormat, GLenum destType, GLint level);
 
 private:
-    void initializeExtensions();
+    Extensions3DUtil(blink::WebGraphicsContext3D*);
+    bool initializeExtensions();
 
     blink::WebGraphicsContext3D* m_context;
     HashSet<String> m_enabledExtensions;
     HashSet<String> m_requestableExtensions;
 };
 
 } // namespace WebCore
 
 #endif // Extensions3DUtil_h