Support for multiple VideoCall.Listeners for a VideoCall.

The current code assumes that only a single instance of VideoCall will be
provided to the default system InCall UI.  Ideally multiple
InCallService implementations should be able to use the VideoCall APIs.
Note: it only really makes sense for a single InCallService to get/set
the video surfaces.

- Fixed bug in ParcelableCall which would cause a new instance of
VideoCallImpl to be created every time a call is updated from Telecom.
Added a flag to ParcelableCall to indicate whether the parcel includes a
change to the video provider information, which is used when unparceling
to determine whether to set/create the video call impl.
- Renamed "setVideoCallback" to "addVideocallback".
- Modified Connection.VideoProvider code to keep a list of Video callbacks
and fire off all of them when Video Provider changes occur.

Bug: 20092420
Change-Id: Ic16b6afe1b7532cc64d006c133adbae57946d97d

telecomm/java/android/telecom/RemoteConnection.java

@@ -311,7 +311,7 @@ public final class RemoteConnection {
         public VideoProvider(IVideoProvider videoProviderBinder) {
             mVideoProviderBinder = videoProviderBinder;
             try {
-                mVideoProviderBinder.setVideoCallback(mVideoCallbackServant.getStub().asBinder());
+                mVideoProviderBinder.addVideoCallback(mVideoCallbackServant.getStub().asBinder());
             } catch (RemoteException e) {
             }
         }