Add script to remove prefixed CSS from third_party/polymer.

third_party/polymer/v1_0/components-chromium/paper-checkbox/paper-checkbox.html

Index: third_party/polymer/v1_0/components-chromium/paper-checkbox/paper-checkbox.html
diff --git a/third_party/polymer/v1_0/components-chromium/paper-checkbox/paper-checkbox.html b/third_party/polymer/v1_0/components-chromium/paper-checkbox/paper-checkbox.html
index 0f53b7f6b1514b47c0f5bfcef8b488df6888f8b8..bcec1a08f24edf12537e2ac5884b622794f278da 100644
--- a/third_party/polymer/v1_0/components-chromium/paper-checkbox/paper-checkbox.html
+++ b/third_party/polymer/v1_0/components-chromium/paper-checkbox/paper-checkbox.html
@@ -106,24 +106,14 @@ Custom property | Description | Default
         border-color: var(--paper-checkbox-unchecked-color, --primary-text-color);
         border-radius: 2px;
         pointer-events: none;
-        -webkit-transition: background-color 140ms, border-color 140ms;
         transition: background-color 140ms, border-color 140ms;
       }
 
       /* checkbox checked animations */
       #checkbox.checked #checkmark {
-        -webkit-animation: checkmark-expand 140ms ease-out forwards;
         animation: checkmark-expand 140ms ease-out forwards;
       }
 
-      @-webkit-keyframes checkmark-expand {
-        0% {
-          -webkit-transform: scale(0, 0) rotate(45deg);
-        }
-        100% {
-          -webkit-transform: scale(1, 1) rotate(45deg);
-        }
-      }
 
       @keyframes checkmark-expand {
         0% {
@@ -150,12 +140,10 @@ Custom property | Description | Default
         border-bottom-width: calc(2/15 * var(--calculated-paper-checkbox-size));
         border-color: var(--paper-checkbox-checkmark-color, white);
         transform-origin: 97% 86%;
-        -webkit-transform-origin: 97% 86%;
       }
 
       :host-context([dir="rtl"]) #checkmark {
         transform-origin: 50% 14%;
-        -webkit-transform-origin: 50% 14%;
       }
 
       /* label */