Add DCHECK to MaskedViewTargeter::GetHitTestMask() overrides

ui/views/masked_view_targeter.h

 // Copyright 2014 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_VIEWS_MASKED_VIEW_TARGETER_H_
 #define UI_VIEWS_MASKED_VIEW_TARGETER_H_
 
 #include "ui/views/view_targeter.h"
 #include "ui/views/views_export.h"
 
@@ skipping 10 matching lines @@
 class VIEWS_EXPORT MaskedViewTargeter : public ViewTargeter {
  public:
   explicit MaskedViewTargeter(View* masked_view);
   virtual ~MaskedViewTargeter();
 
   // Sets the hit-test mask for |view| in |mask| (in |view|'s local
   // coordinate system). Returns whether a valid mask has been set in |mask|.
   virtual bool GetHitTestMask(const View* view, gfx::Path* mask) const = 0;
 
  protected:
+  const View* masked_view() const { return masked_view_; }
+
   // ui::EventTargeter:
   virtual bool EventLocationInsideBounds(
       ui::EventTarget* target,
       const ui::LocatedEvent& event) const OVERRIDE;
 
  private:
   View* masked_view_;
 
   DISALLOW_COPY_AND_ASSIGN(MaskedViewTargeter);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MASKED_VIEW_TARGETER_H_