Make zoom filter independent of the layer size.

ui/compositor/layer.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_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 162 matching lines @@
   // Change the grayscale of all pixels from this layer by this amount.
   // This effect will get "combined" with the inverted, saturate
   // and brightness setting.
   float layer_grayscale() const { return layer_grayscale_; }
   void SetLayerGrayscale(float grayscale);
 
   // Return the target grayscale if animator is running, or the current
   // grayscale otherwise.
   float GetTargetGrayscale() const;
 
-  // Zoom the background by a factor of |zoom|.  The upper left corner of the
-  // zoomed area is offset from the top left corner of the layer by |x_offset|
-  // and |y_offset|.  The effect is blended along the edge across |inset|
-  // pixels.
-  void SetBackgroundZoom(float x_offset, float y_offset, float zoom, int inset);
+  // Zoom the background by a factor of |zoom|. The effect is blended along the
+  // edge across |inset| pixels.
+  void SetBackgroundZoom(float zoom, int inset);
 
   // Invert the layer.
   bool layer_inverted() const { return layer_inverted_; }
   void SetLayerInverted(bool inverted);
 
   // Return the target opacity if animator is running, or the current opacity
   // otherwise.
   float GetTargetOpacity() const;
 
   // Set a layer mask for a layer.
@@ skipping 216 matching lines @@
   float layer_grayscale_;
   bool layer_inverted_;
 
   // The associated mask layer with this layer.
   Layer* layer_mask_;
   // The back link from the mask layer to it's associated masked layer.
   // We keep this reference for the case that if the mask layer gets deleted
   // while attached to the main layer before the main layer is deleted.
   Layer* layer_mask_back_link_;
 
-  // When the layer is zoomed, this is the offset to the upper left corner of
-  // the area in the layer that is zoomed.
-  float zoom_x_offset_;
-  float zoom_y_offset_;
-
   // The zoom factor to scale the layer by.  Zooming is disabled when this is
   // set to 1.
   float zoom_;
 
   // Width of the border in pixels, where the scaling is blended.
   int zoom_inset_;
 
   std::string name_;
 
   LayerDelegate* delegate_;
@@ skipping 22 matching lines @@
   // The size of the delegated frame in DIP, set when SetDelegatedFrame was
   // called.
   gfx::Size delegated_frame_size_in_dip_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_