Selection API: Some functions should throw InvalidNodeTypeError and IndexSizeError.

third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * 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.
@@ skipping 2351 matching lines @@
       this._prompt.on(UI.TextPrompt.TextChangedEvent, this._applyFreeFlowStyleTextEdit.bind(this));
 
     var proxyElement = this._prompt.attachAndStartEditing(selectElement, blurListener.bind(this, context));
     this._navigateToSource(selectElement, true);
 
     proxyElement.addEventListener('keydown', this._editingNameValueKeyDown.bind(this, context), false);
     proxyElement.addEventListener('keypress', this._editingNameValueKeyPress.bind(this, context), false);
     if (isEditingName)
       proxyElement.addEventListener('paste', pasteHandler.bind(this, context), false);
 
-    selectElement.getComponentSelection().setBaseAndExtent(selectElement, 0, selectElement, 1);
+    selectElement.getComponentSelection().setBaseAndExtent(
+        selectElement, 0, selectElement, selectElement.firstChild ? 1 : 0);
   }
 
   /**
    * @param {!Elements.StylePropertyTreeElement.Context} context
    * @param {!Event} event
    */
   _editingNameValueKeyDown(context, event) {
     if (event.handled)
       return;
 
@@ skipping 697 matching lines @@
   }
 
   /**
    * @override
    * @return {!UI.ToolbarItem}
    */
   item() {
     return this._button;
   }
 };