transitional tag to delete canary branch

Merge branch 'master' into release

Merge branch 'master' into release

Merge branch 'master' into release

Merge branch 'master' into release

Merge branch 'master' into release

Merge branch 'master' into release

Merge branch 'master' into release

 - Ensure vsync is instantiated before extensions (ampproject#942)

  - Promise.all polyfill (ampproject#935)
  - fix gulp autofix (ampproject#932)
  - Separate tools distribution from the rest (ampproject#929)
  - Set cookie for the root path and update description (ampproject#928)
  - Experiments.html page for our CDN (ampproject#923)
  - Case-insensitive sanitizing of attribute values (ampproject#917)

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