Send multiple scheduler frame timelines (fix).

Fix the revert and added extra unit test asserts (fail on previous CL
but passes on this CL!!).

Bug: 198192508
Bug: 204941507
Test: atest EventThreadTest; atest ChoreographerNativeTest

Change-Id: Ib9d8df901fab72cae2cee86692d983c6e02d9c2c