🚮 Sweep experiments

Sweep experiments last flipped globally up to 2019-12-04:

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