Clean up deactivate mess

Both onDocumentKeyDown and onViewTabClick would check
this.activating and invoke deactivate() differently depending
on its value. That's ugly, so incorporate the "don't show a dialog
if deactivating during activation" logic into deactivate() itself.

Rename the override parameter to noDialog, and fix the broken
logic around it (it overrode too much).

Also move setting this.activating = false; out of these event
handlers into cancel(), where it clearly belongs because
activatingDeferred is being rejected there.

Change-Id: I6c040c74d36f829128a175f00d4e712dd19d31a7
Merge "Clean up deactivate mess"