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: 3e572433 am: c68d564c

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

Change-Id: Id1546f64f960852982f7a44068e53fa22bbf62d5