Remove deprecated .pre-mp6 styles.

Also, fix some random whitespace to bring Jetpack and WPCOM into sync.

Merges r103985-wpcom.
Merge commit 'b6c8082'
Twenty Fourteen: Reset top margin adjustment for subsequent posts added by Infinite Scroll.

Merges r103932-wpcom.
REST API: Upload Media endpoint: Add errors to the result.

+ Add an errors array in the response with the failures.
+ Return the error directly for single uploads.
+ Add emptyfile for testing purposes.

See: http://[private link]

Merges r103826-wpcom.
JSON API: Most Jetpack sites' XML-RPC URLs are not accessible via HTTPS.

Use the site's home URL to guess if its XML-RPC URL can be served via HTTPS.

Override this for WordPress.com sites via filter.

http://[private link]

[91385]

Merges r103913-wpcom.
JSON API: Fix handling of too-deeply nested comments.

http://[private link]#comment-1853

WordPress hierarchy walkers typically display too-deeply nested objects at the end of the entire list.

The `Walker_Comment` class is an exception: it displays too-deeply nested comments beside their closest ancestor that is not too-deeply nested.

Copy the `Walker_Comment::display_element()` method into the `WPCOM_JSON_API_List_Comments_Walker` class.

https://core.trac.wordpress.org/browser/tags/3.9.2/src/wp-includes/comment-template.php#L1621

Merges r103886-wpcom.
icalendar: Don't try and parse out a Timezone if there is no indication one exits.

Merges r103933-wpcom.