Merge upstream master

Main changes:

* Modifyied the test helpers and added more tests.
* Made BoringSSL error handling a bit safer when unexpected things
  happen.
* Cleaned up NativeRef a bit

Bug: 19820349
Test: cts -m CtsLibcoreTestCases
Change-Id: If539b07ca57e0a4bd408a0dbc2cddbfe2b6d5f50