DevTools: cleanup occurences of selection.getRangeAt to avoid NPE

third_party/WebKit/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 260 matching lines @@
             node: node,
             offset: offset
         };
     },
 
     /**
      * @param {?Selection} selection
      */
     _updateSelectionModel: function(selection)
     {
-        if (!selection || !selection.rangeCount || selection.isCollapsed) {
+        var range = selection && selection.rangeCount ? selection.getRangeAt(0) : null;
+        if (!range || selection.isCollapsed) {
             this._headSelection = null;
             this._anchorSelection = null;
             return false;
         }
 
         var firstSelected = Number.MAX_VALUE;
         var lastSelected = -1;
 
-        var range = selection.getRangeAt(0);
         var hasVisibleSelection = false;
         for (var i = 0; i < this._renderedItems.length; ++i) {
             if (range.intersectsNode(this._renderedItems[i].element())) {
                 var index = i + this._firstVisibleIndex;
                 firstSelected = Math.min(firstSelected, index);
                 lastSelected = Math.max(lastSelected, index);
                 hasVisibleSelection = true;
             }
         }
         if (hasVisibleSelection) {
@@ skipping 336 matching lines @@
 
     /**
      * @return {number}
      */
     _visibleHeight: function()
     {
         // Use offsetHeight instead of clientHeight to avoid being affected by horizontal scroll.
         return this.element.offsetHeight;
     }
 }