Add script to remove prefixed CSS from third_party/polymer.

third_party/polymer/v1_0/components-chromium/iron-autogrow-textarea/iron-autogrow-textarea.html

Index: third_party/polymer/v1_0/components-chromium/iron-autogrow-textarea/iron-autogrow-textarea.html
diff --git a/third_party/polymer/v1_0/components-chromium/iron-autogrow-textarea/iron-autogrow-textarea.html b/third_party/polymer/v1_0/components-chromium/iron-autogrow-textarea/iron-autogrow-textarea.html
index aac2019efaaa73d693fd50d73c1f2166816abc94..5dc7e3f2c89bf21c62e7af31b8abf3ea5e43f231 100644
--- a/third_party/polymer/v1_0/components-chromium/iron-autogrow-textarea/iron-autogrow-textarea.html
+++ b/third_party/polymer/v1_0/components-chromium/iron-autogrow-textarea/iron-autogrow-textarea.html
@@ -44,7 +44,6 @@ Custom property | Description | Default
         width: 400px;
         border: 1px solid;
         padding: 2px;
-        -moz-appearance: textarea;
         -webkit-appearance: textarea;
         overflow: hidden;
       }
@@ -79,21 +78,11 @@ Custom property | Description | Default
         box-shadow: none;
       }
 
-      textarea::-webkit-input-placeholder {
         @apply(--iron-autogrow-textarea-placeholder);
       }
 
-      textarea:-moz-placeholder {
-        @apply(--iron-autogrow-textarea-placeholder);
-      }
 
-      textarea::-moz-placeholder {
-        @apply(--iron-autogrow-textarea-placeholder);
-      }
 
-      textarea:-ms-input-placeholder {
-        @apply(--iron-autogrow-textarea-placeholder);
-      }
     </style>
 
     <!-- the mirror sizes the input/textarea so it grows with typing -->