Camera3: log a warning when frame drop occurs

Bug: 28311997
Change-Id: I7253fb040c1f08c18fc7a01042503e9457163a1e
diff --git a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
index bc8f631..3aff684 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
@@ -271,6 +271,7 @@
      */
     if (buffer.status == CAMERA3_BUFFER_STATUS_ERROR) {
         // Cancel buffer
+        ALOGW("A frame is dropped for stream %d", mId);
         res = currentConsumer->cancelBuffer(currentConsumer.get(),
                 container_of(buffer.buffer, ANativeWindowBuffer, handle),
                 anwReleaseFence);