Try again to fix issue #6912004:tap on gmail notification sends me to home screen

Add a new call to the activity manager to tell it when the activity
is resumed, so it can mark its state as dirty then instead of when
it first tries to create it.

Also tweak things to update the LRU list for the upcoming activity
at the point we start pausing the current activity, to avoid an
inefficiency where we may decide to kill the process of the upcoming
activity if it is at the end of the LRU list.

Change-Id: Ia6dc8c34dc6d4b085a1efbe3a5d5f47721d55078