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

ui/views/widget/native_widget_mac.h

Index: ui/views/widget/native_widget_mac.h
diff --git a/ui/views/widget/native_widget_mac.h b/ui/views/widget/native_widget_mac.h
index c09e8e5c1f5ba842190a12a821ee324bdaa20e15..2fd3bbc93892db60e9720a93a266fb3dbf05c7c6 100644
--- a/ui/views/widget/native_widget_mac.h
+++ b/ui/views/widget/native_widget_mac.h
@@ -10,6 +10,7 @@
 
 namespace views {
 namespace test {
+class HitTestNativeWidgetMac;
 class MockNativeWidgetMac;
 }
 
@@ -132,6 +133,7 @@ class VIEWS_EXPORT NativeWidgetMac : public internal::NativeWidgetPrivate {
 
  private:
   friend class test::MockNativeWidgetMac;
+  friend class test::HitTestNativeWidgetMac;
 
   internal::NativeWidgetDelegate* delegate_;
   scoped_ptr<BridgedNativeWidget> bridge_;