In order to synchronize message id when a new connection is made,
message Id is added as a return value. Also the last posted message Id
is given as paramter, when observer is notfied of new messages.
Bug: 112203066
Change-Id: Ic3921fd176aec1abc7de3ea88c730ad46182d28f
Bufferpool clients are notified bufferpool events via FMQ messages.
Usually the messages are processed by pipeline via piggybacking. To
ensure process FMQ messages even if the process is in idle state,
Observer hidl interface is added. Buffer invalidation caused by
pipleline completion uses Observer interface in order to invalidate
buffers after all normal operations are finished.
Bug: 112203066
Change-Id: I2a4a172d78c6bcedcc809c559321929ebc91c30d
