[View] Clear Hardware-Layers before system destroys HardwareRenderer​.

Symptom: Sometimes HardwareLayer display is corrupted.

Root Cause: In some cases, ViewRootImpl destroys HardwareRenderer​ without
clearing HardwareLayers in the view hirarchy. If the system trims memory fully
and kill the glContext at the same time, HardwareLayer may corrupt.

Solution: Clear Hardware-Layers before system destroys HardwareRenderer​.

Reproduce steps: Modify the cache's trim memory mechanism to make it easier to
trim fully, HardwareLayers implemented in app will easily be corrupted.
Modification of the cache is not required but make it easier to reproduce.

Change-Id: If57c802cdacf8dc37cbbcc199e74f9482834f981
[ActivityManager] Ensure alive process is not killedByAm.

Symptom: Unable to kill by Am again and will be skipped updating its oom adj.

Root Cause:
A restarted process will reuse original process record.
The flag killedByAm will keep previous state.

Solution:
Reset the flag killedByAm to false when the process is started.

Note: Found another similiar patch If95137d91939cc44882ad2813131bcde0edd0c1b

Change-Id: I59a86648ca8d0aed4c489d92751af120aae5ef90