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

third_party/polymer/v1_0/components/paper-checkbox/paper-checkbox.css

 /*
 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
 */
 
 :host {
@@ skipping 11 matching lines @@
 
 #checkboxContainer {
   display: inline-block;
   position: relative;
   width: 18px;
   height: 18px;
   cursor: pointer;
   -webkit-transform: translateZ(0);
   transform: translateZ(0);
   vertical-align: middle;
+  background-color: var(--paper-checkbox-unchecked-background-color, transparent);
 }
 
 :host #ink {
   position: absolute;
   top: -15px;
   left: -15px;
   width: 48px;
   height: 48px;
   color: var(--paper-checkbox-unchecked-ink-color, --primary-text-color);
   opacity: 0.6;
+  pointer-events: none;
 }
 
 :host #ink[checked] {
   color: var(--paper-checkbox-checked-ink-color, --default-primary-color);
 }
 
 :host #checkbox {
   position: relative;
   box-sizing: border-box;
   height: 100%;
@@ skipping 52 matching lines @@
   position: absolute;
   top: -1px;
   left: 4px;
   width: 5px;
   height: 10px;
   border-style: solid;
   border-top: none;
   border-left: none;
   border-right-width: 2px;
   border-bottom-width: 2px;
-  border-color: white;
+  border-color: var(--paper-checkbox-checkmark-color, white);
 }
 
 /* label */
 #checkboxLabel {
   position: relative;
   display: inline-block;
   vertical-align: middle;
   padding-left: 8px;
   white-space: normal;
   pointer-events: none;
@@ skipping 15 matching lines @@
 }
 
 :host([disabled][checked]) #checkbox {
   background-color: var(--paper-checkbox-unchecked-color, --primary-text-color);
   opacity: 0.5;
 }
 
 :host([disabled]) #checkboxLabel  {
   opacity: 0.65;
 }