Make HasRepresentation() work better for vector images.

ui/gfx/image/image_skia_source.h

Index: ui/gfx/image/image_skia_source.h
diff --git a/ui/gfx/image/image_skia_source.h b/ui/gfx/image/image_skia_source.h
index 6250032292bd74c97dbde10b25c7a173c50cf774..9c50760edb6b9d833c85ef193d567eadf2c4a528 100644
--- a/ui/gfx/image/image_skia_source.h
+++ b/ui/gfx/image/image_skia_source.h
@@ -15,13 +15,17 @@ 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