Rename mash_shell to mash_session.

mash/shell/public/interfaces/shell.mojom

Index: mash/shell/public/interfaces/shell.mojom
diff --git a/mash/shell/public/interfaces/shell.mojom b/mash/shell/public/interfaces/shell.mojom
deleted file mode 100644
index 77d1e80a12ba75b422fd91f55693f26cf73bd7f5..0000000000000000000000000000000000000000
--- a/mash/shell/public/interfaces/shell.mojom
+++ /dev/null
@@ -1,19 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-module mash.shell.mojom;
-
-interface ScreenlockStateListener {
-  // This method is called when the listener is initially added with the current
-  // lock state, and subsequently whenever the lock state changes.
-  ScreenlockStateChanged(bool locked);
-};
-
-interface Shell {
-  Logout();
-  SwitchUser();
-  LockScreen();
-  UnlockScreen();
-  AddScreenlockStateListener(ScreenlockStateListener listener);
-};