Add the partial screen magnifier to Chrome OS.

ui/compositor/layer.h

Index: ui/compositor/layer.h
diff --git a/ui/compositor/layer.h b/ui/compositor/layer.h
index f9fcbc9208246dbb3eb655747676951ea4f70368..61fdb22586450d35fc7495ebbd4212a333b74ae4 100644
--- a/ui/compositor/layer.h
+++ b/ui/compositor/layer.h
@@ -168,6 +168,9 @@ class COMPOSITOR_EXPORT Layer
   // grayscale otherwise.
   float GetTargetGrayscale() const;
 
+  // Zoom the background by this amount.
+  void SetBackgroundZoom(float x_offset, float y_offset, float zoom, int inset);
+
   // Invert the layer.
   bool layer_inverted() const { return layer_inverted_; }
   void SetLayerInverted(bool inverted);
@@ -326,6 +329,9 @@ class COMPOSITOR_EXPORT Layer
   // Set all filters which got applied to the layer.
   void SetLayerFilters();
 
+  // Set all filters which got applied to the layer background.
+  void SetLayerBackgroundFilters();
+
   const LayerType type_;
 
   Compositor* compositor_;
@@ -372,6 +378,18 @@ class COMPOSITOR_EXPORT Layer
   // 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_;