Write new visual diff tests for AMP components owned by @aghassemi

[rsimha]

The following components owned by @aghassemi do not have visual diff test coverage.

• amp-video
• amp-vimeo
• amp-youtube
• amp-app-banner
• amp-fx-parallax
• amp-lightbox
• amp-lightbox-viewer
• amp-viz-vega
• amp-form
• amp-facebook
• amp-social-share
• amp-izlesene
• amp-nexxtv-player
• amp-gist

How to add a visual test:

1. Create a simple test page for your component. You could use a portion of an existing page in examples/, or create a new one based on AMP by Example.
2. Create a new directory in examples/visual-tests, for the test page (+ assets)
3. Add an entry for the test page to test/visual-diff/visual-tests.json
4. Create a PR and wait for it to be tested on Travis (the percy/amphtml check will fail)
   
5. Click the details link and approve the Percy build that was generated on your PR branch
   
6. Merge your PR and approve the next Percy build on master. Until you do so, master will be red, and this is expected.
   

Tip: Use #11413 as an example of how to add a new visual test. If your test page needs time to reach a steady state before a snapshot is taken, you can specify css classes that need to be visible, eventually appear, or eventually disappear. See test/visual-diff/visual-tests.json for examples.

Documentation: See this page on the AMP developer guide.

Master issue: #10155

[ampprojectbot]

This issue doesn't have a category which makes it harder for us to keep track of it. @aghassemi Please add an appropriate category.

[ampprojectbot]

This issue hasn't been updated in awhile. @aghassemi Do you have any updates?

[aghassemi]

/cc @nainar

[ampprojectbot]

This issue hasn't been updated in awhile. @aghassemi Do you have any updates?