Currently, setAlpha was using mRtTransaction to send the SC transaction.
However, that's also used by positionChanged. This could cause
synchronization issues because both callbacks are invoked from a thread
pool with no synchronization ensured.
Instead, create a Transaction that's used just for FrameCallbacks.
FrameCallbacks will all occur on the same thread so it's safe to use the
same object. Additionally, created a separate transaction that should be
used for positionChanged. This is because it's invoked from a thread
pool can could interfere with the main render thread transactions.
Finally, use the original mRtTransaction only for places that are called
synchronously from renderThread.
Test: Hard to repro original issue. Bubbles works
Bug: 184559328
Change-Id: Ia5a36ad063c19e8a481a57170e47029f7c2c7ee7
f541d037f5