bug fix possible NPE while startProcessLocked()

In case, process doesn't create well while startingProcessLocked().
There is possibility to make NPE.
Setting app's crash handler needs to be assigned after null check routine.

Change-Id: I67fb6427f72d93f79fed36eb44c47d37eafdac31
[ActivityManager] Invalidate last screenshot when activity relaunched

Symptom:
The task thumbnail is not updated when activity relaunched.

Reproduce Steps:
1. Put device in portrait
2. Launch Calculator
3. Launch Recent App (the Calculator's screenshot is correct)
4. Rotate device to landscape
5. Click Calculator in Recent App to return to Calculator (Calculator has relaunched to landsacpe ui)
6. Launch Recent App again (the Calculator's screenshot is not updated)

Change-Id: I92e951ea2ee215c52ca6e50cf6f9e02deb787bce
[ActivityManager] Fix race condition in pss collection

Symptom:
There has a race condition that two threads are accessing
the mPendingPssProcesses simultaneously. One of the thread
is collecting the process pss by looping the mPendingPssProcesses.
The other thread is requesting to collect pss of all processes,
which clears mPendingPssProcesses and adding processes back.

Solution:
Avoid race condition by adding synchornized protection.

Change-Id: Ifb090eda9c4a1b8e3fd980fe0171e9dd77773b46
Merge "[ActivityManager] Invalidate last screenshot when activity relaunched"
Merge "bug fix possible NPE while startProcessLocked()"
Merge "[ActivityManager] Fix race condition in pss collection"