Remove call to no-op EditorView method
Assign atom.lastUncaughtError in window.onerror handler
Perform a sync update after editor becomes visible

This pauses updates during measurements. If any updates were requested
while measuring, we force an update synchronously to prevent flicker.

This commit also removes the visibility check before updating, because
we can't force an update from this spot in the lifecycle. This shouldn't
be needed anyway because we are polling for visibility changes.
Call checkForVisibilityChange when showing editors via EditorView::show/hide
Add regression coverage for remeasuring characters w/ requested update

The problem here is that the lines in the editor no longer reflect the
lines on screen, but we're looking for line nodes corresponding to the
editor's current contents.
Pass tokenizedLines to LinesComponent so measuring stays in sync

Fixes #3318
Update status bar to fix specs
Use RxJS observables for an event and a behavior on Pane
Use getters in pane-spec instead of direct property access
Implement Pane::isActive without behavior
Convert pane-container-spec to not reference raw properties