[DevTools] Consume ToolbarButton click.

third_party/WebKit/Source/devtools/front_end/ui/Toolbar.js

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 497 matching lines @@
     this.element.appendChild(dropdownArrowIcon);
     if (width)
       this.element.style.width = width + 'px';
   }
 
   /**
    * @param {!Event} event
    */
   _clicked(event) {
     this.dispatchEventToListeners(UI.ToolbarButton.Events.Click, event);
+    event.consume();
   }
 
   /**
    * @param {!Event} event
    */
   _mouseDown(event) {
     this.dispatchEventToListeners(UI.ToolbarButton.Events.MouseDown, event);
   }
 
   /**
@@ skipping 376 matching lines @@
     return this.inputElement.checked;
   }
 
   /**
    * @param {boolean} value
    */
   setChecked(value) {
     this.inputElement.checked = value;
   }
 };