tree b65db71be0444e2b7d43245812114fe9cffe1140
parent 9f15ba2e1a42e64e03305500c4179a5ad87b7423
author Garfield Tan <xutan@google.com> 1591325665 -0700
committer Garfield Tan <xutan@google.com> 1591377162 -0700

Use WeakReference to hold target in values.

WeakHashMap holds strong references to values, so if we would like to
have them cleaned up automatically we need make sure we don't reference
the key strongly in the value.

Bug: 149918957
Test: Bubble animation looks OK.
Test: No GC root paths through PhysicsAnimator.
Test: atest PhysicsAnimator
Change-Id: I4e701bfb7f91662e18c317eaf895b5ea31e0860d