base

Implemented frequent read returns for quick stop in time lapse.

If the frame capture interval is large, read will block for a long time.
Due to the way the mediaRecorder framework works, a stop() call from
mediaRecorder waits until the read returns, causing a long wait for
stop() to return. To avoid this, we return a copy of the last read
frame with the same time stamp if a frame is not available quickly.
This keeps the read() call from blocking too long. This method is
triggered when startQuickReadReturns() is called on
CameraSourceTimeLapse.

In the still camera case, also using waitRelative on Condition
instaed of sleeping, so that we can wake it up.
Also for the idle check instead of sleeping, we now wait on a
condition variable, which is woken up when the last takePicture
callback gets called.

Change-Id: Ia74386e175536aee0f44ae2f8b114c353d3d72f5