Heartbeat:
- Use the page visibility API (when available) and document.hasFocus() instead of window.onfocus/onblur. Improves speeding up/slowing down the interval and works for iframes by default.
- Add a setting for minimal interval. Maximum value is 10 min. This overrides all other intervals and cannot be changed after setting it at initialization. Can be used to reduce the frequency of requests on hosts that have low limits for used CPU time, etc.
- Extend the setting of interval to support 120 sec. (60 sec, is still the default).
- Always suspend after one hour of keyboard/mouse/touch inactivity.
Fixes #29779.
Built from https://develop.svn.wordpress.org/trunk@30293


git-svn-id: http://core.svn.wordpress.org/trunk@30292 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: remove strings that are not translated before outputting the translations. Fixes #27797.
Built from https://develop.svn.wordpress.org/trunk@30294


git-svn-id: http://core.svn.wordpress.org/trunk@30293 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix PHP notice in `Tests_Feed_RSS2::test_items()`.

A notice was being thrown when `get_the_tags()` returned false, and `foreach()`
was run over that return value.

See [30283].
Built from https://develop.svn.wordpress.org/trunk@30295


git-svn-id: http://core.svn.wordpress.org/trunk@30294 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: enable direct calls to `_WP_Editors::wp_mce_translation()`. When using TinyMCE directly, this makes it easier to load the translation of the default strings. Fixes #30293.
Built from https://develop.svn.wordpress.org/trunk@30296


git-svn-id: http://core.svn.wordpress.org/trunk@30295 1a063a9b-81f0-0310-95a4-ce76da25c4cd