ui: Eliminate allocating gfx::Canvas on the heap for every view.

ui/gfx/canvas.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_GFX_CANVAS_H_
 #define UI_GFX_CANVAS_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 65 matching lines @@
 
   // Creates canvas with provided DIP |size| and |image_scale|.
   // If this canvas is not opaque, it's explicitly cleared to transparent before
   // being returned.
   Canvas(const Size& size, float image_scale, bool is_opaque);
 
   // Constructs a canvas with the size and the image_scale of the provided
   // |image_rep|, and draws the |image_rep| into it.
   Canvas(const ImageSkiaRep& image_rep, bool is_opaque);
 
-  virtual ~Canvas();
-
   // Creates a Canvas backed by an |sk_canvas| with |image_scale_|.
   // |sk_canvas| is assumed to be already scaled based on |image_scale|
   // so no additional scaling is applied.
-  static Canvas* CreateCanvasWithoutScaling(SkCanvas* sk_canvas,
-                                            float image_scale);
+  Canvas(SkCanvas* sk_canvas, float image_scale);
+
+  virtual ~Canvas();
 
   // Recreates the backing platform canvas with DIP |size| and |image_scale_|.
   // If the canvas is not opaque, it is explicitly cleared.
   // This method is public so that canvas_skia_paint can recreate the platform
   // canvas after having initialized the canvas.
   // TODO(pkotwicz): Push the image_scale into skia::PlatformCanvas such that
   // this method can be private.
   void RecreateBackingCanvas(const Size& size,
                              float image_scale,
                              bool is_opaque);
@@ skipping 303 matching lines @@
                        const FontList& font_list,
                        SkColor color,
                        const Rect& display_rect,
                        int flags);
 
   skia::PlatformCanvas* platform_canvas() { return owned_canvas_.get(); }
   SkCanvas* sk_canvas() { return canvas_; }
   float image_scale() const { return image_scale_; }
 
  private:
-  Canvas(SkCanvas* canvas, float image_scale);
-
   // Test whether the provided rectangle intersects the current clip rect.
   bool IntersectsClipRectInt(int x, int y, int w, int h);
   bool IntersectsClipRect(const Rect& rect);
 
   // Helper for the DrawImageInt functions declared above. The |pixel|
   // parameter if true indicates that the bounds and the image are to
   // be assumed to be in pixels, i.e. no scaling needs to be performed.
   void DrawImageIntHelper(const ImageSkia& image,
                           int src_x,
                           int src_y,
@@ skipping 15 matching lines @@
 
   skia::RefPtr<skia::PlatformCanvas> owned_canvas_;
   SkCanvas* canvas_;
 
   DISALLOW_COPY_AND_ASSIGN(Canvas);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_CANVAS_H_