[Sensors] Improvements in shared buffer managing
This patch adds the following improvements:
-Introduces SeqLock synchronization for shared buffer reads and writes.
- Single sensor shared buffer is guaranteed to have same fixed size on every platform. This is important as our layout tests use fixed sized shared buffer on JS side.
- Introduced common data structures for sensor reading and sensor reading buffer that are used in both blink and platform layers.
For the implementation on Android shared buffer operations moved from java to generic C++ code, same code is to be reused for implementations on other platforms.
BUG=606766
Review-Url: https://codereview.chromium.org/2395853003
Cr-Commit-Position: refs/heads/master@{#424403}
27 files changed
