Add BUILD.gn files for chromecast/media

chromecast/media/base/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.
+
+import("//build/config/crypto.gni")
+import("//chromecast/chromecast.gni")
+
+source_set("base") {
+  sources = [
+    "decrypt_context.cc",
+    "decrypt_context.h",
+    "decrypt_context_clearkey.cc",
+    "decrypt_context_clearkey.h",
+    "key_systems_common.cc",
+    "key_systems_common.h",
+    "media_caps.cc",
+    "media_caps.h",
+    "switching_media_renderer.cc",
+    "switching_media_renderer.h",
+  ]
+
+  deps = [
+    "//base",
+    "//crypto",
+    "//crypto:platform",
+    "//third_party/widevine/cdm:version_h",
+  ]
+
+  configs += [ "//chromecast:config" ]
+
+  if (is_chromecast_chrome_branded) {
+    deps += [
+      # TODO(gyp): add dependency on internal/chromecast_internal:media_base_internal
+    ]
+  } else {
+    sources += [ "key_systems_common_simple.cc" ]
+  }
+}