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 57 matching lines @@
   // Changes the value of GetSupportedScales() to |scales|.
   static void SetSupportedScales(const std::vector<float>& scales);
 
   // Returns a vector with the scale factors which are supported by this
   // platform, in ascending order.
   static const std::vector<float>& GetSupportedScales();
 
   // Returns the maximum scale supported by this platform.
   static float GetMaxSupportedScale();
 
+  // Maps to the closest supported scale. In case scale is greater than the

[msw, 2017/05/24 21:44:18]

nit: This is worded a bit awkwardly; consider something like "Maps to the
closest supported scale. Returns an exact match, a smaller scale within 0.2
units, the nearest larger scale, or the min/max supported scale."

[khmel, 2017/05/26 15:34:53]

Done.

+  // nearest supported scale not more than 0.2 then lowest supported scale is
+  // used otherwise scale is mapped to upper supported scale.
+  static float MapToSupportedScale(float scale);
+
   // Creates an image from the passed in bitmap.
   // DIP width and height are based on scale factor of 1x.
   // Adds ref to passed in bitmap.
   // WARNING: The resulting image will be pixelated when painted on a high
   // density display.
   static ImageSkia CreateFrom1xBitmap(const SkBitmap& bitmap);
 
   // Returns a deep copy of this ImageSkia which has its own storage with
   // the ImageSkiaRep instances that this ImageSkia currently has.
   // This can be safely passed to and manipulated by another thread.
@@ skipping 46 matching lines @@
   gfx::Size size() const;
 
   // Returns pointer to 1x bitmap contained by this object. If there is no 1x
   // bitmap, the bitmap whose scale factor is closest to 1x is returned.
   // This function should only be used in unittests and on platforms which do
   // not support scale factors other than 1x.
   // TODO(pkotwicz): Return null SkBitmap when the object has no 1x bitmap.
   const SkBitmap* bitmap() const { return &GetBitmap(); }
 
   // Returns a vector with the image reps contained in this object.
-  // There is no guarantee that this will return all images rep for
+  // There is no guarantee that this will r+images rep for

[msw, 2017/05/24 21:44:18]

fix

[khmel, 2017/05/26 15:34:53]

Done.

   // 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;
 
  private:
   friend class test::TestOnThread;
@@ skipping 15 matching lines @@
   // 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_