tree cb5c58af5a678e522aa224a8ef39fa9434bfe9d6
parent 0751e29195ed8c880d657ec2919f359920091a86
author Bonian Chen <bonianchen@google.com> 1576077762 +0800
committer Bonian Chen <bonianchen@google.com> 1576241005 +0800

[Settings] Enabling first stage of threading

Settings app would move PreferenceController to run
in background thread in the near future.

To support this, change some of the design within these
essential components to allow:
1. Handler to run on non-main thread
2. Minimum multi-thread reentrance support

Bug: 146045802
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=GlobalSettingsChangeListenerTest
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=ActiveSubsciptionsListenerTest
Change-Id: Ica5c942b919007d7d260feee632752d3353a6f18