Remove unneeded files from third_party/polymer.

third_party/polymer/v1_0/components-chromium/paper-menu/CONTRIBUTING.md

-
-<!--
-This file is autogenerated based on
-https://github.com/PolymerElements/ContributionGuide/blob/master/CONTRIBUTING.md
-
-If you edit that file, it will get updated everywhere else.
-If you edit this file, your changes will get overridden :)
--->
-# Polymer Elements
-## Guide for Contributors
-
-Polymer Elements are built in the open, and the Polymer authors eagerly encourage any and all forms of community contribution. When contributing, please follow these guidelines:
-
-### Filing Issues
-
-**If you are filing an issue to request a feature**, please provide a clear description of the feature. It can be helpful to describe answers to the following questions:
-
- 1. **Who will use the feature?** _“As someone filling out a form…”_
- 2. **When will they use the feature?** _“When I enter an invalid value…”_
- 3. **What is the user’s goal?** _“I want to be visually notified that the value needs to be corrected…”_
-
-**If you are filing an issue to report a bug**, please provide:
-
- 1. **A clear description of the bug and related expectations.** Consider using the following example template for reporting a bug:
-
- ```markdown
- The `paper-foo` element causes the page to turn pink when clicked.
-
- ## Expected outcome
-
- The page stays the same color.
-
- ## Actual outcome
-
- The page turns pink.
-
- ## Steps to reproduce
-
- 1. Put a `paper-foo` element in the page.
- 2. Open the page in a web browser.
- 3. Click the `paper-foo` element.
- ```
-
- 2. **A reduced test case that demonstrates the problem.** If possible, please include the test case as a JSBin. Start with this template to easily import and use relevant Polymer Elements: [http://jsbin.com/cagaye](http://jsbin.com/cagaye/edit?html,output).
-
- 3. **A list of browsers where the problem occurs.** This can be skipped if the problem is the same across all browsers.
-
-### Submitting Pull Requests
-
-**Before creating a pull request**, please ensure that an issue exists for the corresponding change in the pull request that you intend to make. **If an issue does not exist, please create one per the guidelines above**. The goal is to discuss the design and necessity of the proposed change with Polymer authors and community before diving into a pull request.
-
-When submitting pull requests, please provide:
-
- 1. **A reference to the corresponding issue** or issues that will be closed by the pull request. Please refer to these issues using the following syntax:
-
- ```markdown
- (For a single issue)
- Fixes #20
-
- (For multiple issues)
- Fixes #32, #40
- ```
-
- 2. **A succinct description of the design** used to fix any related issues. For example:
-
- ```markdown
- This fixes #20 by removing styles that leaked which would cause the page to turn pink whenever `paper-foo` is clicked.
- ```
-
- 3. **At least one test for each bug fixed or feature added** as part of the pull request. Pull requests that fix bugs or add features without accompanying tests will not be considered.
-
-If a proposed change contains multiple commits, please [squash commits](https://www.google.com/url?q=http://blog.steveklabnik.com/posts/2012-11-08-how-to-squash-commits-in-a-github-pull-request) to as few as is necessary to succinctly express the change. A Polymer author can help you squash commits, so don’t be afraid to ask us if you need help with that!