Introduce cc::LocalFrameId and use in SurfaceFactory

cc/ipc/local_frame_id.mojom

Index: cc/ipc/local_frame_id.mojom
diff --git a/cc/ipc/local_frame_id.mojom b/cc/ipc/local_frame_id.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..feca9b0fcc1471e96d1d499078e8bd1108df8eac
--- /dev/null
+++ b/cc/ipc/local_frame_id.mojom
@@ -0,0 +1,16 @@
+// 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 cc.mojom;
+
+struct LocalFrameId {
+  // An identifier allocated by the client uniquely identifying a surface within
+  // a client process.
+  uint32 local_id;
+
+  // A cryptographically secure random int chosen to make the LocalFrameId
+  // unguessable by other clients.
+  uint64 nonce;
+};
+