DevTools: do not discard soft context menu on glass pane mouseup unconditionally.

Source/devtools/front_end/ui/SoftContextMenu.js

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 311 matching lines @@
             break;
         }
         event.consume(true);
     },
 
     _glassPaneMouseUp: function(event)
     {
         // Return if this is simple 'click', since dispatched on glass pane, can't use 'click' event.
         if (new Date().getTime() - this._time < 300)
             return;
+        if (event.target === this.element)
+            return;
         this._discardMenu(true, event);
         event.consume();
     },
 
     /**
      * @param {boolean} closeParentMenus
      * @param {!Event=} event
      */
     _discardMenu: function(closeParentMenus, event)
     {
@@ skipping 28 matching lines @@
 
     _discardSubMenus: function()
     {
         if (this._subMenu)
             this._subMenu._discardSubMenus();
         this._contextMenuElement.remove();
         if (this._parentMenu)
             delete this._parentMenu._subMenu;
     }
 }