Add basic daily active use logging.

src/platform/metrics/session_states.h

Index: src/platform/metrics/session_states.h
diff --git a/src/platform/metrics/session_states.h b/src/platform/metrics/session_states.h
new file mode 100644
index 0000000000000000000000000000000000000000..293dbd995cf8f2ab044ff4cb35a84decd5738bfd
--- /dev/null
+++ b/src/platform/metrics/session_states.h
@@ -0,0 +1,17 @@
+// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// A table of user session states, to be included when building tabular things.
+//
+// See network_states.h for details.
+
+
+#ifndef STATE
+#define STATE(name, capname)
+#endif
+
+STATE(started, Started)
+STATE(stopped, Stopped)
+
+#undef STATE