Pass a ui::PaintContext from ui::Layer to layer delegates.

ui/aura/window_delegate.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_AURA_WINDOW_DELEGATE_H_
 #define UI_AURA_WINDOW_DELEGATE_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "ui/aura/aura_export.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_handler.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
 class Canvas;
 class Path;
 class Point;
 class Rect;
 class Size;
 }
 
 namespace ui {
 class GestureEvent;
 class KeyEvent;
 class Layer;
 class MouseEvent;
+class PaintContext;
 class TextInputClient;
 class Texture;
 class TouchEvent;
 }
 
 namespace aura {
 
 // Delegate interface for aura::Window.
 class AURA_EXPORT WindowDelegate : public ui::EventHandler {
  public:
@@ skipping 24 matching lines @@
   virtual bool ShouldDescendIntoChildForEventHandling(
       Window* child,
       const gfx::Point& location) = 0;
 
   // Returns true of the window can be focused.
   virtual bool CanFocus() = 0;
 
   // Invoked when mouse capture is lost on the window.
   virtual void OnCaptureLost() = 0;
 
-  // Asks the delegate to paint window contents into the supplied canvas.
-  virtual void OnPaint(gfx::Canvas* canvas) = 0;
+  // Asks the delegate to paint window contents into the supplied context.
+  virtual void OnPaint(const ui::PaintContext& context) = 0;
 
   // Called when the window's device scale factor has changed.
   virtual void OnDeviceScaleFactorChanged(float device_scale_factor) = 0;
 
   // Called from Window's destructor before OnWindowDestroyed and before the
   // children have been destroyed and the window has been removed from its
   // parent.
   // This method takes the window because the delegate implementation may no
   // longer have a route back to the window by the time this method is called.
   virtual void OnWindowDestroying(Window* window) = 0;
@@ skipping 21 matching lines @@
   // above returns true.
   virtual void GetHitTestMask(gfx::Path* mask) const = 0;
 
  protected:
   ~WindowDelegate() override {}
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_DELEGATE_H_