Remove amp-youtube from AMPHTML Ads spec

[lannka]

The current amp-youtube implementation relies on a cross-origin iframe which brings uncertainty to the performance of the ad. In general, AMPHTML ads tries to avoid any use of cross-origin iframe. Here we propose to deprecate the use of amp-youtube in AMPHTML ads. To follow the deprecation policy, here is the list of checkboxes:

• Allow for at least 2 weeks of open discussion.
• Wait for 3 approvals from core committers.
• Update spec
• Announce change on the mailing list.
• Start warning for ads that might break via the developer console.
• Give developers 6 weeks to apply changes. (8/23/2019)
• Update validator
• Remove the warning

/cc @keithwrightbos @aghassemi @jasti @honeybadgerdontcare

[honeybadgerdontcare]

Is this the i2i to satisfy the deprecation policy?

[lannka]

@honeybadgerdontcare good point. Updated the issue to follow the process.

[lannka]

@ampproject/wg-ads @ampproject/a4a @ampproject/ads

[yazdotdev]

@lannka @honeybadgerdontcare by the way, the placeholder image for amp youtube is jpg and not webp. any chance of changing this? it might be more a youtube team rather than amp team issue though.

[lannka]

@yazdotdev thanks for bringing it up. I created a separate issue to discuss this #21357

[honeybadgerdontcare]

@lannka I approve this of this change

[lannka]

thanks @honeybadgerdontcare
collecting more stamps: @keithwrightbos @aghassemi @jasti @zhouyx

[jasti]

Approved!

[jeffkaufman]

strongly in favor

[calebcordry]

@lannka Are we ready to announce this change on the mailing list?

[lannka]

Announced here: https://groups.google.com/forum/m/#!topic/amphtml-announce/_CU2TF1bpfM