Context menu on views must show on mouse down for non-WIN.

ui/views/widget/widget.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_VIEWS_WIDGET_WIDGET_H_
 #define UI_VIEWS_WIDGET_WIDGET_H_
 
 #include <set>
 #include <stack>
 #include <vector>
@@ skipping 440 matching lines @@
   // A secondary widget is one that is automatically closed (via Close()) when
   // all non-secondary widgets are closed.
   // Default is true.
   // TODO(beng): This is an ugly API, should be handled implicitly via
   //             transience.
   void set_is_secondary_widget(bool is_secondary_widget) {
     is_secondary_widget_ = is_secondary_widget;
   }
   bool is_secondary_widget() const { return is_secondary_widget_; }
 
+  void set_is_mouse_button_pressed(bool is_mouse_button_pressed) {
+    is_mouse_button_pressed_ = is_mouse_button_pressed;
+  }
+
   // Returns whether the Widget is visible to the user.
   virtual bool IsVisible() const;
 
   // Returns the ThemeProvider that provides theme resources for this Widget.
   virtual ui::ThemeProvider* GetThemeProvider() const;
 
   ui::NativeTheme* GetNativeTheme() {
     return const_cast<ui::NativeTheme*>(
         const_cast<const Widget*>(this)->GetNativeTheme());
   }
@@ skipping 376 matching lines @@
   // True when window movement via mouse interaction with the frame should be
   // disabled.
   bool movement_disabled_;
 
   DISALLOW_COPY_AND_ASSIGN(Widget);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_WIDGET_H_