Rely solely on transient activation for orientation events

[marcoscaceres]

Please see:
whatwg/html#8490

• At least two implementers are interested (and none opposed):
  • Chrome implements this behavior (in that they special case screen orientation change events to call .requestFullscreen()).
  • …
• Tests are written and can be reviewed and commented upon at:
  • …
• Implementation bugs are filed:
  • Chromium: …
  • Gecko: …
  • WebKit: …
• MDN issue is filed: …

(See WHATWG Working Mode: Changes for more details.)

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Preview | Diff

[marcoscaceres]

@foolip, the "triggered by a user generated orientation change" was underspecified and only implemented in Chrome. We are trying to address this issue in an interoperable manner in whatwg/html#8490

However, Screen Orientation no longer defines "triggered by a user generated orientation change" so that doesn't make sense anymore in the FS spec (i.e., it doesn't link to anything anymore).

[marcoscaceres]

To be clear, there is interest to align WebKit with Chromium's behavior... but we need to specify this properly in HTML and then hook full screen API properly once that's done (independently of this PR).