Camera: implement buffer managment API

Test: compile
Bug: 109829698
Change-Id: I3d95792282da52db9db6fd6a086bbd7b3ff9dca9
diff --git a/services/camera/libcameraservice/device3/Camera3Stream.cpp b/services/camera/libcameraservice/device3/Camera3Stream.cpp
index ee989e1..0a30a97 100644
--- a/services/camera/libcameraservice/device3/Camera3Stream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3Stream.cpp
@@ -795,6 +795,12 @@
     return hasOutstandingBuffersLocked();
 }
 
+size_t Camera3Stream::getOutstandingBuffersCount() const {
+    ATRACE_CALL();
+    Mutex::Autolock l(mLock);
+    return getHandoutOutputBufferCountLocked();
+}
+
 status_t Camera3Stream::setStatusTracker(sp<StatusTracker> statusTracker) {
     Mutex::Autolock l(mLock);
     sp<StatusTracker> oldTracker = mStatusTracker.promote();