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

ui/views/view.h

Index: ui/views/view.h
diff --git a/ui/views/view.h b/ui/views/view.h
index 435d507ca1e8293e8975aeab3bdb6415dc35cda3..2912b9a6784f3a50013462be79714c9fcfa6b655 100644
--- a/ui/views/view.h
+++ b/ui/views/view.h
@@ -791,6 +791,10 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
   // as it is always equal to the current View.
   virtual void ShowContextMenu(const gfx::Point& p, bool is_mouse_gesture);
 
+  // On some platforms, we show context menu on mouse press instead of release.
+  // This method returns true for those platforms.
+  static bool ShouldShowContextMenuOnMousePress();
+
   // Drag and drop -------------------------------------------------------------
 
   DragController* drag_controller() { return drag_controller_; }