Add BUILD.gn files for chromecast/media

chromecast/media/cma/ipc_streamer/BUILD.gn

+# Copyright 2015 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.
+
+source_set("ipc_streamer") {
+  sources = [
+    "audio_decoder_config_marshaller.cc",
+    "audio_decoder_config_marshaller.h",
+    "av_streamer_proxy.cc",
+    "av_streamer_proxy.h",
+    "coded_frame_provider_host.cc",
+    "coded_frame_provider_host.h",
+    "decoder_buffer_base_marshaller.cc",
+    "decoder_buffer_base_marshaller.h",
+    "decrypt_config_marshaller.cc",
+    "decrypt_config_marshaller.h",
+    "video_decoder_config_marshaller.cc",
+    "video_decoder_config_marshaller.h",
+  ]
+
+  deps = [
+    "//base",
+    "//chromecast/media/cma/base",
+    "//media",
+  ]
+
+  configs += [ "//chromecast:config" ]
+}