Update bower.json for Polymer elements and add PRESUBMIT.py

third_party/polymer/v1_0/components/paper-tabs/paper-tabs.html

 <!--
 @license
 Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
 This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 Code distributed by Google as part of the polymer project is also
 subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 -->
 
@@ skipping 440 matching lines @@
           this.$.tabsContainer.scrollLeft += l;
         }
       }
     },
 
     _calcPercent: function(w, w0) {
       return 100 * w / w0;
     },
 
     _positionBar: function(width, left) {
+      width = width || 0;
+      left = left || 0;
+
       this._width = width;
       this._left = left;
       this.transform(
           'translate3d(' + left + '%, 0, 0) scaleX(' + (width / 100) + ')',
           this.$.selectionBar);
     },
 
     _onBarTransitionEnd: function(e) {
       var cl = this.$.selectionBar.classList;
       // bar animation: expand -> contract
       if (cl.contains('expand')) {
         cl.remove('expand');
         cl.add('contract');
         this._positionBar(this._pos.width, this._pos.left);
       // bar animation done
       } else if (cl.contains('contract')) {
         cl.remove('contract');
       }
     }
 
   });
 
 </script>