Dismiss keyguard when resuming visible activities

If an activity is visible behind the keyguard when it is launched
by another activity then there would be no call to dismissKeyguard.
Because the other activity is pausing the call to dismissKeyguard
is skipped in startActivityLocked(). And because it is already
visible the call to ActivityRecord.windowsVisible() is never made and
the call to reportActivityVisibleLocked() which calls
dismissKeyguard() is also never made.

This change recognizes when an activity is resumed and visible and
calls dismissKeyguard() in that case.

Fixes bug 10732489.

Change-Id: I3de1350a55231aaa14dadc8709fd0fcf4960742c