Merge "Cache weak reference for static context." into sc-dev am: f7d20b35...

Merge "Cache weak reference for static context." into sc-dev am: f7d20b35 am: 199a5df6 am: 2b7a3d47

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15245990

Change-Id: I25638736de1cea93d1ddd4f80213378fbb6eb01f