Camera3: Add more tracing

Change-Id: I5f5d0d3f37244f19446c473db70373bdf16cce56
diff --git a/services/camera/libcameraservice/camera3/Camera3Stream.cpp b/services/camera/libcameraservice/camera3/Camera3Stream.cpp
index f05658a..ab563df 100644
--- a/services/camera/libcameraservice/camera3/Camera3Stream.cpp
+++ b/services/camera/libcameraservice/camera3/Camera3Stream.cpp
@@ -312,8 +312,10 @@
         // Got all buffers, register with HAL
         ALOGV("%s: Registering %d buffers with camera HAL",
                 __FUNCTION__, bufferCount);
+        ATRACE_BEGIN("camera3->register_stream_buffers");
         res = hal3Device->ops->register_stream_buffers(hal3Device,
                 &bufferSet);
+        ATRACE_END();
     }
 
     // Return all valid buffers to stream, in ERROR state to indicate