Bring back Event, and wait on Event rather than on Execution.

This is at the recommendation of the API council.

This undoes change I50b8e155d9589210e14920237878a4f295e7755f

Bug: 63905942
Test: nn/runtime/test

Change-Id: I5922f13ae7070f7ec0af035557a9921c88ca9221
5 files changed
tree: c9d6dbfe391cc1139458b14a8ff50a6b5d1c95dc
  1. common/
  2. driver/
  3. runtime/
  4. tools/
  5. Android.bp
  6. README.txt