Remove third_party/polymer from .gitignore

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" value="foo/bar"></iron-meta>
-```
-
-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('value');
-```
-
-Pure imperative form would be like:
-
-```javascript
-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('value');
-```