Fix a JNI local reference leak in MediaDrm

A reference leak was found in the subtitle usecase that also
applies to android_media_MediaDrm.cpp
(Code taken from the similar fix in android_media_MediaPlayer.cpp)

Change-Id: Icc4b25e4adc9a600ff4ac99a7a8478bb55a6e348
Fix visibility of multiple non-fullscreen activities.

Issue detail:
Assume X, Y are non-fullscreen activities.
 a.Home starts an activity X in task A in application stack.
 b.X starts an activity Y in <task A> or <new task B>
 c.Activity X will be invisible.

How to fix:
Because the function "isActivityOverHome" means an activity is able to see home.
But there may have many non-fullscreen activities between the top non-fullscreen activity and home.
If flag "behindFullscreen" is set, those middle activities will be invisible.
So it should only take care from who is adjacent to home.
Then check two flags frontOfTask(task root) and mOnTopOfHome for constraining the condition.

Change-Id: I60bcea304976414e44835a0a38675aae365e9e19
Cursor leakage due to cancellation signal

If a query call was cancelled, the cursor adaptor might leak. The
adaptor is now closed if any exception is thrown during query.

Change-Id: Ic4c2edeaf2fcef56b4ef59484a36d3233aa12dbc
libs/hwui: fix memory leakage

Change-Id: Idba22f76b42cd1ad474a052d63f703d6472bdd39
Signed-off-by: zwliew <zhaoweiliew@gmail.com>