Invalidate all wallpaper cache if display configuration changed

ash/desktop_background/user_wallpaper_delegate.h

 // Copyright 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 ASH_DESKTOP_BACKGROUND_USER_WALLPAPER_DELEGATE_H_
 #define ASH_DESKTOP_BACKGROUND_USER_WALLPAPER_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "ui/views/corewm/window_animations.h"
 
@@ skipping 13 matching lines @@
 
   // Sets wallpaper animation duration in ms. Pass 0 to use the default.
   virtual void SetAnimationDurationOverride(int animation_duration_in_ms) = 0;
 
   // Should the slower initial animation be shown (as opposed to the faster
   // animation that's used e.g. when switching from one user's wallpaper to
   // another's on the login screen)?
   virtual bool ShouldShowInitialAnimation() = 0;
 
   // Updates current wallpaper. It may switch the size of wallpaper based on the
-  // current display's resolution.
-  virtual void UpdateWallpaper() = 0;
+  // current display's resolution. If |clear_cache| is true, all wallpaper
+  // cache should be cleared. This is required when screen size changes to a
+  // larger size and we need to load a larger resolution wallpaper. All the
+  // previous small resolution wallpaper cache should be cleared.

[oshima, 2014/03/13 22:23:40]

I think the comment is still not clear because screen size changes when you
change the UI scaling or rotate. Can you explicitly say the display's native
resolution (or pixel resolution) has changed?

[bshe, 2014/03/13 23:19:04]

Used native resolution to be more specific.

On 2014/03/13 22:23:40, oshima wrote:

+  virtual void UpdateWallpaper(bool clear_cache) = 0;
 
   // Initialize wallpaper.
   virtual void InitializeWallpaper() = 0;
 
   // Opens the set wallpaper page in the browser.
   virtual void OpenSetWallpaperPage() = 0;
 
   // Returns true if user can open set wallpaper page. Only guest user returns
   // false currently.
   virtual bool CanOpenSetWallpaperPage() = 0;
 
   // Notifies delegate that wallpaper animation has finished.
   virtual void OnWallpaperAnimationFinished() = 0;
 
   // Notifies delegate that wallpaper boot animation has finished.
   virtual void OnWallpaperBootAnimationFinished() = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_DESKTOP_BACKGROUND_USER_WALLPAPER_DELEGATE_H_