Use WeakHashMap for MotionRuntime's target-based caches (#78)

Authored by randcode-generator on Mon, Apr 24, 6:19 PM.

Description

Use WeakHashMap for MotionRuntime's target-based caches (#78)

Summary:
Use WeakHashMap instead of SimpleArrayMap

Fixes https://github.com/material-motion/material-motion-android/issues/76

Reviewers: O2 Material Motion, O6 Material Android platform reviewers, Material Motion, markwei

Reviewed By: O2 Material Motion, O6 Material Android platform reviewers, Material Motion, markwei

Tags: Material Motion

Differential Revision: http://codereview.cc/D3102