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 e353448bff4dea61b8e44038a4039f3982b47972..4a67a469564955ed10243557168feaea8e50ecc1 100644
--- a/ui/views/view.h
+++ b/ui/views/view.h
@@ -790,6 +790,10 @@ 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_; }