Merge pull request ampproject#2183 from cramforce/creative-id

Do not leak the fact that an ad slot could not be filled through the creative id.

Merge pull request ampproject#2180 from dvoytenko/fixes47

Defer overflow:auto on a iframe container

Fix reference error.

Merge pull request ampproject#2082 from dvoytenko/access42

RFC: Multiple login links for access

Merge pull request ampproject#2128 from dvoytenko/fixed1

RFC: position:fixed elements are always in layers

Merge pull request ampproject#2166 from cramforce/things-now-validate

vimeo, dailymotion and soundcloud now validate.

Merge tag '1455859169598' into release

Merge pull request ampproject#1960 from mkhatib/debug-amp-video-bug

Monitor amp-youtube player state

transitional tag to delete canary branch

Merge tag '1455773092418' into release