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

third_party/polymer/v1_0/components/iron-meta/README.md

 iron-meta
 =========
 
 `iron-meta` is a generic element you can use for sharing information across the DOM tree.
 It uses [monostate pattern](http://c2.com/cgi/wiki?MonostatePattern) such that any
 instance of iron-meta has access to the shared
 information. You can use `iron-meta` to share whatever you want (or create an extension
 [like x-meta] for enhancements).
 
 The `iron-meta` instances containing your actual data can be loaded in an import,
 or constructed in any way you see fit. The only requirement is that you create them
 before you try to access them.
 
 Examples:
 
 If I create an instance like this:
 
 ```html
-<iron-meta key="info" keyUrl="foo/bar"></iron-meta>
+<iron-meta key="info" value="foo/bar"></iron-meta>
 ```
 
-Note that keyUrl="foo/bar" is the metadata I've defined. I could define more
+Note that value="foo/bar" is the metadata I've defined. I could define more
 attributes or use child nodes to define additional metadata.
 
 Now I can access that element (and it's metadata) from any iron-meta instance
 via the byKey method, e.g.
 
 ```javascript
-meta.byKey('info').getAttribute('keyUrl').
+meta.byKey('info').getAttribute('value');
 ```
 
 Pure imperative form would be like:
 
 ```javascript
-document.createElement('iron-meta').byKey('info').getAttribute('keyUrl');
+document.createElement('iron-meta').byKey('info').getAttribute('value');
 ```
 
 Or, in a Polymer element, you can include a meta in your template:
 
 ```html
 <iron-meta id="meta"></iron-meta>
 ```
 
 ```javascript
-this.$.meta.byKey('info').getAttribute('keyUrl');
+this.$.meta.byKey('info').getAttribute('value');
 ```