Makes iframe transport work with SERP (ampproject#11988)

* Accomodates SERP iframe arrangement

* Uses getTopWindow

* Typo

fixing style merge conflicts (ampproject#11897)

InOb should accept threshold with single number (ampproject#11891)

* threshold accept single number

* fix percy

postquare AMP embed (ampproject#11517)

* Engageya AMP

Engageya AMP

* fixed indentation

fixed indentation

* postquare

* postquare

* fixed postquare md file

* fixed indentations

* fixed small issues according to the review

Fix bug that useRemoteHtml wasn't being used in Doubleclick-a4a-config (

ampproject#11794)

* Actually use useRemoteHtml param

* Check for RTC

 amp-twitter: tighten up fallback logic so it does not pick up random…

… numbers. (ampproject#11761)

report i-amphtml-no-boilerplate experiment (ampproject#11729)

Validator rollup (ampproject#11638)

* update AMP Story rules

* Allow viewport-fit meta viewport content property.

* update style[amp-keyframes] rules

* Update to CSS SYNTAX message.

* Fix amp keyframes.

Add the core amp-story component (ampproject#11511)

* Add the core amp-story component

* Add TODO LDAP

* Update amp-story.css

* Update amp-story.js

* Fix eslint errors in amp-story.js and add back experiment

* Fix lint errors in test-amp-story.js

* amp-story.js lint changes

* Update test-amp-story.js

* Update amp-story.js

* Update amp-story.js

* Add @const where possible.

* Add fixes for various integration points that broke during merges.

* Remove renamed 'AnalyticsTrigger'

* Add missing trailing comma to test file

* Update closure type annotations.

* Remove double nullability indicators

* Explicitly import animation typedefs.

* Update typedefs for animation-types

* Partial fixes for closure type issues

* Partial fixes for closure type issues (part 2)

* Partial fixes for closure type issues (part 3)

* Remove extra whitespace

* Partial fixes for closure type issues (part 4)

* Fix missing imports and typos

* Fix missing imports and typos

* Fix remaining type issues

* Skip failing amp-story tests; fix loading screen when no elements require loading.

Skip AMP article visual test (ampproject#11497)