Add editor component resize spec
Add the simplest resize fix that will work.
Move scroll view measurements to componentWillUpdate
Don't perform an update in response scroll view dimension changes

We always measure the scroll view in the ::componentWillUpdate hook, so
performing *another* update in response to the measurement causes an
invariant violation in react. Whenever we are measuring, we are always
already updating.
Update editor height change spec
Add a div that triggers overflowchanged events on resize
Remove suppressUpdates
Remove width setting of overflowExpander
Use polling to detect editor resize
Remove measureScrollView helper
Request scrollView measurement on resize events
Merge remote-tracking branch 'origin/master' into cj-expose-resizing-to-editor
Merge pull request #2603 from atom/cj-expose-resizing-to-editor

Expose resizing to editor