[ntp4] Apply style tweaks so that bookmarks page scrolls correctly.

chrome/browser/resources/ntp4/tile_page.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('ntp4', function() {
   'use strict';
 
   // We can't pass the currently dragging tile via dataTransfer because of
   // http://crbug.com/31037
   var currentlyDraggingTile = null;
@@ skipping 775 matching lines @@
     },
 
     /**
      * Does the work of calculating the visibility, height and position of the
      * scrollbar thumb (there is no track or buttons).
      */
     doUpdateScrollbars_: function() {
       this.scrollbarUpdate_ = 0;
 
       var content = this.content_;
-      if (content.scrollHeight == content.clientHeight) {
+
+      // Adjust height to account for possible header-bar.
+      var adjustedClientHeight = content.clientHeight - content.offsetTop;
+
+      if (content.scrollHeight == adjustedClientHeight) {
         this.scrollbar_.hidden = true;
         return;
       } else {
         this.scrollbar_.hidden = false;
       }
 
-      var thumbTop = content.scrollTop / content.scrollHeight *
-          this.clientHeight;
-      var thumbHeight = content.clientHeight / content.scrollHeight *
+      var thumbTop = content.offsetTop +
+          content.scrollTop / content.scrollHeight * adjustedClientHeight;
+      var thumbHeight = adjustedClientHeight / content.scrollHeight *
           this.clientHeight;
 
       this.scrollbar_.style.top = thumbTop + 'px';
       this.scrollbar_.style.height = thumbHeight + 'px';
     },
 
     /**
      * Get the height for a tile of a certain width. Override this function to
      * get non-square tiles.
      * @param {number} width The pixel width of a tile.
@@ skipping 189 matching lines @@
      */
     tileMoved: function(draggedTile) {
     },
   };
 
   return {
     getCurrentlyDraggingTile: getCurrentlyDraggingTile,
     TilePage: TilePage,
   };
 });