Implement hit tests/client area.

ui/aura/mus/window_tree_host_mus_delegate.h

 // Copyright 2016 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_MUS_WINDOW_TREE_HOST_MUS_DELEGATE_H_
 #define UI_AURA_MUS_WINDOW_TREE_HOST_MUS_DELEGATE_H_
 
 #include "ui/aura/aura_export.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace aura {
 
 class WindowPortMus;
 class WindowTreeHostMus;
 
 class AURA_EXPORT WindowTreeHostMusDelegate {
  public:
   // Called when the bounds of a WindowTreeHostMus is about to change.
   // |bounds| is the bounds supplied to WindowTreeHostMus::SetBounds() and is
   // in screen pixel coordinates.
   virtual void OnWindowTreeHostBoundsWillChange(
       WindowTreeHostMus* window_tree_host,
       const gfx::Rect& bounds) = 0;
 
+  // Called when the client area of a WindowTreeHostMus is about to change.
+  virtual void OnWindowTreeHostClientAreaWillChange(
+      WindowTreeHostMus* window_tree_host,
+      const gfx::Insets& insets) = 0;
+
+  // Called when the hit test mask is about to be cleared.
+  virtual void OnWindowTreeHostClearHitTestMask(

[sky, 2016/11/19 15:29:31]

How about a single function for this that takes a const gfx::Rect* null means
clear?

[Elliot Glaysher, 2016/11/22 00:48:07]

Done.

+      WindowTreeHostMus* window_tree_host) = 0;
+
+  // Called when the hit test mask is about to be cleared.
+  virtual void OnWindowTreeHostHitTestMaskWillChange(
+      WindowTreeHostMus* window_tree_host,
+      const gfx::Rect& mask_rect) = 0;
+
   // Called when a WindowTreeHostMus is created without a WindowPort.
   virtual std::unique_ptr<WindowPortMus> CreateWindowPortForTopLevel() = 0;
 
   // Called from WindowTreeHostMus's constructor once the Window has been
   // created.
   virtual void OnWindowTreeHostCreated(WindowTreeHostMus* window_tree_host) = 0;
 
  protected:
   virtual ~WindowTreeHostMusDelegate() {}
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_WINDOW_TREE_HOST_MUS_DELEGATE_H_