Add copyright headers DM.

Review URL: https://codereview.chromium.org/1037713003
diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index 364afe0..1c56be7 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -1,3 +1,10 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
 #ifndef DMSrcSink_DEFINED
 #define DMSrcSink_DEFINED