Add SurfaceSequence mojom file to cc/ipc and edit corresponding GYP file

cc/ipc/surface_sequence.mojom

Index: cc/ipc/surface_sequence.mojom
diff --git a/cc/ipc/surface_sequence.mojom b/cc/ipc/surface_sequence.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..631fe8d7a6107ad86372cc787456a27723d3bd5f
--- /dev/null
+++ b/cc/ipc/surface_sequence.mojom
@@ -0,0 +1,15 @@
+// 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;
+
+// A per-surface-namespace sequence number that's used to coordinate
+// dependencies between frames. A sequence number may be satisfied once, and
+// may be depended on once.
+// A surface sequence consists of an id namespace and a local sequence number.
+struct SurfaceSequence {
+  uint32 id_namespace;
+  uint32 sequence;
+};
+