🚮 Sweep experiments

Sweep experiments last flipped globally up to 2019-12-06:

- (2018-07-23, ampproject#17012) amp-access-iframe: 1
- (2019-10-01, ampproject#24810) amp-action-macro: 1
- (2019-11-08, ampproject#25480) amp-mega-menu: 1
- (2019-11-13, ampproject#25516) amp-nested-menu: 1
- (2017-02-07, ampproject#7403) amp-playbuzz: 1
- (2019-10-21, ampproject#25170) amp-sidebar-swipe-to-dismiss: 1
- (2018-11-05, ampproject#19140) amp-story-responsive-units: 1
- (2018-07-11, ampproject#16678) amp-story-v1: 1
- (2018-07-11, ampproject#16678) chunked-amp: 1
- (2019-10-28, ampproject#25269) fix-inconsistent-responsive-height-selection: 0
- (2019-02-26, ampproject#21058) fixed-elements-in-lightbox: 1
- (2017-05-16, ampproject#9298) pump-early-frame: 1
- (2019-11-12, ampproject#25512) swg-gpay-native: 1

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**⚠️ This changes Javascript source files**

The following may contain errors and/or require intervention to remove superfluous conditionals:

- `extensions/amp-access/0.1/amp-access-source.js`
- `extensions/amp-access/0.1/test/test-amp-access-source.js`
- `extensions/amp-action-macro/0.1/amp-action-macro.js`
- `extensions/amp-action-macro/0.1/test/test-amp-action-macro.js`
- `extensions/amp-playbuzz/0.1/amp-playbuzz.js`
- `extensions/amp-playbuzz/0.1/test/test-amp-playbuzz.js`
- `extensions/amp-sidebar/0.1/amp-sidebar.js`
- `extensions/amp-sidebar/0.2/amp-sidebar.js`
- `extensions/amp-story/1.0/amp-story.js`
- `extensions/amp-story/1.0/test/test-amp-story.js`
- `src/runtime.js`
- `test/unit/test-runtime.js`