arc: Support non-standard display scale factors.

ui/gfx/image/image_skia.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_H_
 #define UI_GFX_IMAGE_IMAGE_SKIA_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 132 matching lines @@
   // Returns a vector with the image reps contained in this object.
   // There is no guarantee that this will return all images rep for
   // supported scale factors.
   std::vector<gfx::ImageSkiaRep> image_reps() const;
 
   // When the source is available, generates all ImageReps for
   // supported scale factors. This method is defined as const as
   // the state change in the storage is agnostic to the caller.
   void EnsureRepsForSupportedScales() const;
 
+  // Clears cached representations for non-supported scale factors that are
+  // based on |scale|.
+  void RemoveUnsupportedRepresentationsForScale(float scale);
+
  private:
   friend class test::TestOnThread;
   FRIEND_TEST_ALL_PREFIXES(ImageSkiaTest, EmptyOnThreadTest);
   FRIEND_TEST_ALL_PREFIXES(ImageSkiaTest, StaticOnThreadTest);
   FRIEND_TEST_ALL_PREFIXES(ImageSkiaTest, SourceOnThreadTest);
 
   // Initialize ImageSkiaStorage with passed in parameters.
   // If the image rep's bitmap is empty, ImageStorage is set to NULL.
   void Init(const gfx::ImageSkiaRep& image_rep);
 
   const SkBitmap& GetBitmap() const;
 
   // Checks if the current thread can read/modify the ImageSkia.
   bool CanRead() const;
   bool CanModify() const;
 
   // Detach the storage from the currently assinged thread
   // so that other thread can access the storage.
   void DetachStorageFromThread();
 
   // A refptr so that ImageRepSkia can be copied cheaply.
   scoped_refptr<internal::ImageSkiaStorage> storage_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_IMAGE_IMAGE_SKIA_H_