Makes ImageView do a bit more checking before assuming images equal

ui/views/controls/image_view.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_VIEWS_CONTROLS_IMAGE_VIEW_H_
 #define UI_VIEWS_CONTROLS_IMAGE_VIEW_H_
 
 #include "ui/gfx/image/image_skia.h"
 #include "ui/views/view.h"
 
@@ skipping 66 matching lines @@
 
   // Overriden from View:
   virtual gfx::Size GetPreferredSize() OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
   virtual void GetAccessibleState(ui::AccessibleViewState* state) OVERRIDE;
   virtual bool GetTooltipText(const gfx::Point& p,
                               string16* tooltip) const OVERRIDE;
   virtual bool HitTestRect(const gfx::Rect& rect) const OVERRIDE;
 
  private:
+  // Returns true if |img| is the same as the last image we painted. This is
+  // intended to be a quick check, not exhaustive. In other words it's possible
+  // for this to return false even though the images are in fact equal.
+  bool IsImageEqual(const gfx::ImageSkia& img) const;
+
   // Compute the image origin given the desired size and the receiver alignment
   // properties.
   gfx::Point ComputeImageOrigin(const gfx::Size& image_size) const;
 
   // Whether the image size is set.
   bool image_size_set_;
 
   // The actual image size.
   gfx::Size image_size_;
 
   // The underlying image.
   gfx::ImageSkia image_;
 
   // Horizontal alignment.
   Alignment horiz_alignment_;
 
   // Vertical alignment.
   Alignment vert_alignment_;
 
   // The current tooltip text.
   string16 tooltip_text_;
 
   // A flag controlling hit test handling for interactivity.
   bool interactive_;
 
+  // Scale last painted at.
+  float last_paint_scale_;
+
+  // Address of bytes we last painted. This is used only for comparison, so its
+  // safe to cache.
+  void* last_painted_bitmap_pixels_;
+
   DISALLOW_COPY_AND_ASSIGN(ImageView);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_IMAGE_VIEW_H_