[MacViews] Enable dragging a window by its caption/draggable areas.

ui/views/widget/native_widget_mac.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_WIDGET_NATIVE_WIDGET_MAC_H_
 #define UI_VIEWS_WIDGET_NATIVE_WIDGET_MAC_H_
 
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/widget/native_widget_private.h"
 
 namespace views {
 namespace test {
+class HitTestNativeWidgetMac;
 class MockNativeWidgetMac;
 }
 
 class BridgedNativeWidget;
 
 class VIEWS_EXPORT NativeWidgetMac : public internal::NativeWidgetPrivate {
  public:
   NativeWidgetMac(internal::NativeWidgetDelegate* delegate);
   ~NativeWidgetMac() override;
 
@@ skipping 98 matching lines @@
 
  protected:
   // Creates the NSWindow that will be passed to the BridgedNativeWidget.
   // Called by InitNativeWidget. The return value will be autoreleased.
   virtual gfx::NativeWindow CreateNSWindow(const Widget::InitParams& params);
 
   internal::NativeWidgetDelegate* delegate() { return delegate_; }
 
  private:
   friend class test::MockNativeWidgetMac;
+  friend class test::HitTestNativeWidgetMac;
 
   internal::NativeWidgetDelegate* delegate_;
   scoped_ptr<BridgedNativeWidget> bridge_;
 
   Widget::InitParams::Ownership ownership_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMac);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_NATIVE_WIDGET_MAC_H_