Some minor polishing.

Change-Id: I2e8f2bf3671e9676f115aaa894684618087e979d
diff --git a/tools/emulator/system/camera/CallbackNotifier.cpp b/tools/emulator/system/camera/CallbackNotifier.cpp
index e6ec37e..a877b40 100755
--- a/tools/emulator/system/camera/CallbackNotifier.cpp
+++ b/tools/emulator/system/camera/CallbackNotifier.cpp
@@ -234,7 +234,8 @@
             mNotifyCB(CAMERA_MSG_RAW_IMAGE_NOTIFY, 0, 0, mCBOpaque);
         }
         if (isMessageEnabled(CAMERA_MSG_COMPRESSED_IMAGE)) {
-            /* Compress the frame to JPEG. TODO: Make sure that frame is NV21! */
+            /* Compress the frame to JPEG. Note that when taking pictures, we
+             * have requested camera device to provide us with NV21 frames. */
             NV21JpegCompressor compressor;
             status_t res =
                 compressor.compressRawImage(frame, camera_dev->getFrameWidth(),