Add the copresence component.

components/copresence/BUILD.gn

Index: components/copresence/BUILD.gn
diff --git a/components/copresence/BUILD.gn b/components/copresence/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..cb0a5f32f6f11add0d47b608aa3a1497e57444ff
--- /dev/null
+++ b/components/copresence/BUILD.gn
@@ -0,0 +1,20 @@
+# Copyright 2014 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.
+
+static_library("copresence") {
+  sources = [
+    "copresence_client.cc",
+    "public/copresence_client_delegate.h",
+    "public/copresence_client.h",
+    "public/whispernet_client.h",
+    "rpc/rpc_handler.cc",
+    "rpc/rpc_handler.h",
+  ]
+
+  deps = [
+    "//base",
+    "//components/copresence/proto",
+    "//net",
+  ]
+}