Add BUILD.gn files for chromecast/media

chromecast/base/BUILD.gn

Index: chromecast/base/BUILD.gn
diff --git a/third_party/mojo/src/mojo/public/interfaces/bindings/BUILD.gn b/chromecast/base/BUILD.gn
similarity index 64%
copy from third_party/mojo/src/mojo/public/interfaces/bindings/BUILD.gn
copy to chromecast/base/BUILD.gn
index cf8a1183d70bfb3fc3bac1d9571ae357ef0669d0..b105a71926ae9424d9f0374f7586faebd648e411 100644
--- a/third_party/mojo/src/mojo/public/interfaces/bindings/BUILD.gn
+++ b/chromecast/base/BUILD.gn
@@ -2,10 +2,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("../../tools/bindings/mojom.gni")
-
-mojom("bindings") {
+source_set("base") {
   sources = [
-    "interface_control_messages.mojom",
+    "cast_paths.cc",
+    "cast_paths.h",
   ]
+
+  configs += [ "//chromecast:config" ]
 }