[pinpoint] Add iron-form and paper-checkbox to polymer components.

third_party/polymer/components/iron-form/README.md

+
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+
+[![Build status](https://travis-ci.org/PolymerElements/iron-form.svg?branch=master)](https://travis-ci.org/PolymerElements/iron-form)
+
+_[Demo and API docs](https://elements.polymer-project.org/elements/iron-form)_
+
+
+##&lt;iron-form&gt;
+
+`<iron-form>` is an HTML `<form>` element that can validate and submit any custom
+elements that implement `Polymer.IronFormElementBehavior`, as well as any
+native HTML elements. For more information on which attributes are
+available on the native form element, see [https://developer.mozilla.org/en-US/docs/Web/HTML/Element/form](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/form)
+
+It supports both `get` and `post` methods, and uses an `iron-ajax` element to
+submit the form data to the action URL.
+
+  Example:
+
+```html
+<form is="iron-form" id="form" method="post" action="/form/handler">
+  <paper-input name="name" label="name"></paper-input>
+  <input name="address">
+  ...
+</form>
+```
+
+By default, a native `<button>` element will submit this form. However, if you
+want to submit it from a custom element's click handler, you need to explicitly
+call the form's `submit` method.
+
+  Example:
+
+```html
+<paper-button raised onclick="submitForm()">Submit</paper-button>
+
+function submitForm() {
+  document.getElementById('form').submit();
+}
+```
+
+To customize the request sent to the server, you can listen to the `iron-form-presubmit`
+event, and modify the form's[`iron-ajax`](https://elements.polymer-project.org/elements/iron-ajax)
+object. However, If you want to not use `iron-ajax` at all, you can cancel the
+event and do your own custom submission:
+
+  Example of modifying the request, but still using the build-in form submission:
+
+```javascript
+form.addEventListener('iron-form-presubmit', function() {
+  this.request.method = 'put';
+  this.request.params = someCustomParams;
+});
+```
+
+  Example of bypassing the build-in form submission:
+
+```javascript
+form.addEventListener('iron-form-presubmit', function(event) {
+  event.preventDefault();
+  var firebase = new Firebase(form.getAttribute('action'));
+  firebase.set(form.serialize());
+});
+```
+
+