Android: Add common function for adding/releasing native reference

This CL introduces common functions for adding and releasing
native references to reduce the number of JNI functions.

BUG=webrtc:8043

Review-Url: https://codereview.webrtc.org/3003213002
Cr-Original-Commit-Position: refs/heads/master@{#19547}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: b1c7453bfa4c7d369069e6dd77e849994f0f1427
18 files changed