Make HasRepresentation() work better for vector images.

ui/gfx/image/image_skia_source.h

 // Copyright (c) 2012 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 UI_GFX_IMAGE_IMAGE_SKIA_SOURCE_H_
 #define UI_GFX_IMAGE_IMAGE_SKIA_SOURCE_H_
 
 #include <vector>
 
 #include "ui/gfx/gfx_export.h"
 
 namespace gfx {
 
 class ImageSkiaRep;
 
 class GFX_EXPORT ImageSkiaSource {
  public:
-  virtual ~ImageSkiaSource() {}
+  virtual ~ImageSkiaSource();
 
   // Returns the ImageSkiaRep for the given |scale|. ImageSkia caches the
   // returned ImageSkiaRep and calls this method only if it doesn't have
   // ImageSkiaRep for given |scale|. There is no need for the implementation to
   // cache the image.
   virtual gfx::ImageSkiaRep GetImageForScale(float scale) = 0;
+
+  // Subclasses should override this to return true when they are capable of
+  // providing an exact representation at any desired scale factor.
+  virtual bool HasRepresentationAtAllScales() const;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_IMAGE_IMAGE_SKIA_SOURCE_H_