Analytics: expose visibility API (ampproject#8787)

* Expose visibility API

* Analytics: expose visibility API

Fix race condition in service registration (ampproject#8720)

Fix image-lightbox resize issue in ios 10.3 (ampproject#8687)

Unblocking the master on Edge (ampproject#8680)

Revert "don't queue more than one schedule call (ampproject#8475)" (a…

…mpproject#8639)

This reverts commit 0885e2c.

Prevent errors during experiment cleanups (ampproject#8448)

* Catch experiment cleanup mishaps by making sure config changes are not accompanied by other changes.

* Exit code 1 when an error is detected.

* Remove non-config changes. This travis run should pass.

* Remove exception for pr-check.js. This travis run may fail, but it's what we want to submit.

* Debugging info for files and build targets.

* Exclude config files from build-system.

* Exclude config files from build-system.

* Remove exception for pr-check.js.

* Temporarily allow pr-check.js. This should pass.

* Add a non config change. This should fail.

* Clean up code for commit.

Fixing WhatsApp social share on iOS 10.3 (ampproject#8486)

Fixing custom scroll-snap on IOS (ampproject#8391)

* Fixing custom scroll-snap on IOS

* More testing.

* Adding IOS_CUSTOM_SNAP_TIMEOUT

* Adding IOS_TOUCH_TIMEOUT

* Bring back experiments and test on all devices.

* lint fix

Fixing custom scroll-snap on IOS (ampproject#8391)

* Fixing custom scroll-snap on IOS

* More testing.

* Adding IOS_CUSTOM_SNAP_TIMEOUT

* Adding IOS_TOUCH_TIMEOUT

* Bring back experiments and test on all devices.

* lint fix

Changes the way AdSense slot format is computed in FF, and adds creat…

…ive centering. (ampproject#8012)

* For AdSense FF, changed format computation to rely on, when available, the slot width/height attributes. Also added creative centering.

* Forgot import statement + removed extraneous space.

* Using slot width and height.

* Fixes #getAdUrl test.

* Lint error.

* Lint error.

* Added three additional tests.

* Added trailing commas to placate linter.

* Added expectations on tag dimensions for new tests + linter fix.

* Missed merge issue.

* Removed unused import.

* Using querySelector.

* Moved styling into css file; removed tests.

* Re-added the tests which now check for the presence of the correct computed styles.

* Unused import.

* Removed some test code.

* Cleaned up tests.