Clean up forward declarations in Source/core/html

Source/core/html/canvas/WebGLCompressedTextureETC1.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 WebGLCompressedTextureETC1_h
 #define WebGLCompressedTextureETC1_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/canvas/WebGLExtension.h"
 #include "wtf/PassRefPtr.h"
 
 namespace blink {
 
-class WebGLTexture;
-
 class WebGLCompressedTextureETC1 FINAL : public WebGLExtension, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<WebGLCompressedTextureETC1> create(WebGLRenderingContextBase*);
     static bool supported(WebGLRenderingContextBase*);
     static const char* extensionName();
 
     virtual ~WebGLCompressedTextureETC1();
     virtual WebGLExtensionName name() const OVERRIDE;
 
 private:
     explicit WebGLCompressedTextureETC1(WebGLRenderingContextBase*);
 };
 
 } // namespace blink
 
 #endif // WebGLCompressedTextureETC1_h