DevTools: Fix illegal argument types in ViewportControl

Source/devtools/front_end/ui/ViewportControl.js

 /*
  * Copyright (C) 2013 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 275 matching lines @@
         }
         this._selectionIsBackward = isBackward;
         return true;
     },
 
     /**
      * @param {?Selection} selection
      */
     _restoreSelection: function(selection)
     {
-        var anchorElement;
+        var anchorElement = null;
         var anchorOffset;
         if (this._firstVisibleIndex <= this._anchorSelection.item && this._anchorSelection.item <= this._lastVisibleIndex) {
             anchorElement = this._anchorSelection.node;
             anchorOffset = this._anchorSelection.offset;
         } else {
             if (this._anchorSelection.item < this._firstVisibleIndex)
                 anchorElement = this._topGapElement;
             else if (this._anchorSelection.item > this._lastVisibleIndex)
                 anchorElement = this._bottomGapElement;
             anchorOffset = this._selectionIsBackward ? 1 : 0;
         }
 
-        var headElement;
+        var headElement = null;
         var headOffset;
         if (this._firstVisibleIndex <= this._headSelection.item && this._headSelection.item <= this._lastVisibleIndex) {
             headElement = this._headSelection.node;
             headOffset = this._headSelection.offset;
         } else {
             if (this._headSelection.item < this._firstVisibleIndex)
                 headElement = this._topGapElement;
             else if (this._headSelection.item > this._lastVisibleIndex)
                 headElement = this._bottomGapElement;
             headOffset = this._selectionIsBackward ? 0 : 1;
@@ skipping 112 matching lines @@
      * @param {!Node} container
      * @param {number} offset
      * @return {number}
      */
     _textOffsetInNode: function(itemElement, container, offset)
     {
         if (!offset)
             return 0;
         var chars = 0;
         var node = itemElement;
-        while ((node = node.traverseNextTextNode(true)) && node !== container)
+        while ((node = node.traverseNextTextNode()) && node !== container)
             chars += node.textContent.length;
         return chars + offset;
     },
 
     /**
      * @param {?Event} event
      */
     _onScroll: function(event)
     {
         this.refresh();
@@ skipping 52 matching lines @@
 
     /**
      * @param {number} index
      */
     forceScrollItemToBeLast: function(index)
     {
         this._rebuildCumulativeHeightsIfNeeded();
         this.element.scrollTop = this._cumulativeHeights[index] - this.element.clientHeight;
     }
 }