Only load theme images for the scale factors that use them

chrome/browser/themes/browser_theme_pack.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 CHROME_BROWSER_THEMES_BROWSER_THEME_PACK_H_
 #define CHROME_BROWSER_THEMES_BROWSER_THEME_PACK_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 72 matching lines @@
 
   // Returns the theme pack image for |id|. Returns an empty image if an image
   // is not found.
   gfx::Image GetImageNamed(int id);
 
   // Returns the raw PNG encoded data for IDR_THEME_NTP_*. This method is only
   // supposed to work for the NTP attribution and background resources.
   base::RefCountedMemory* GetRawData(int id,
                                      ui::ScaleFactor scale_factor) const;
 
+  // Returns the raw PNG encoded data for IDR_THEME_NTP_* for the available
+  // scale factor with the highest scale if available, otherwise NULL.
+  // The corresponding scale factor is returned in |scale_factor|.
+  base::RefCountedMemory* GetRawDataWithHighestScale(
+      int id,
+      ui::ScaleFactor* scale_factor) const;
+
   // Returns the set of image idrs which can be overwritten by a user provided
   // theme.
   static void GetThemeableImageIDRs(std::set<int>* result);
 
   // Whether this theme provides an image for |id|.
   bool HasCustomImage(int id) const;
 
  private:
   friend struct content::BrowserThread::DeleteOnThread<
       content::BrowserThread::FILE>;
@@ skipping 157 matching lines @@
   } *display_properties_;
 
   // A list of included source images. A pointer to a -1 terminated array of
   // our persistent IDs.
   int* source_images_;
 #pragma pack(pop)
 
   // The scale factors represented by the images in the theme pack.
   std::vector<ui::ScaleFactor> scale_factors_;
 
+  // The scale factors ordered by scale from lowest to highest.
+  std::vector<ui::ScaleFactor> scale_factors_ordered_by_scale_;
+
   // References to raw PNG data. This map isn't touched when |data_pack_| is
   // non-NULL; |image_memory_| is only filled during BuildFromExtension(). Any
   // image data that needs to be written to the DataPack during WriteToDisk()
   // needs to be in |image_memory_|.
   RawImages image_memory_;
 
   // Loaded images. These are loaded from |image_memory_|, from |data_pack_|,
   // and by BuildFromExtension(). These images should only be accessed on the UI
   // thread.
   ImageCache images_on_ui_thread_;
 
   // Cache of images created in BuildFromExtension(). Once the theme pack is
   // created, this cache should only be accessed on the file thread. There
   // should be no IDs in |image_memory_| that are in |images_on_file_thread_|
   // or vice versa.
   ImageCache images_on_file_thread_;
 
+  base::WeakPtrFactory<BrowserThemePack> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserThemePack);
 };
 
 #endif  // CHROME_BROWSER_THEMES_BROWSER_THEME_PACK_H_