Adds MediaClientAndroid to support embedder/MediaDrmBridge interaction.

chromecast/media/base/key_systems_common_simple.cc

Index: chromecast/media/base/key_systems_common_simple.cc
diff --git a/chromecast/media/base/key_systems_common_simple.cc b/chromecast/media/base/key_systems_common_simple.cc
index e6dbd02890298d0f97a9cb64240d6b8f47f75c0a..671ce037730f3438631836aea3c2906f97585abe 100644
--- a/chromecast/media/base/key_systems_common_simple.cc
+++ b/chromecast/media/base/key_systems_common_simple.cc
@@ -11,5 +11,13 @@ CastKeySystem GetPlatformKeySystemByName(const std::string& key_system_name) {
   return KEY_SYSTEM_NONE;
 }
 
+#if defined(OS_ANDROID)
+std::vector<::media::MediaClientAndroid::KeySystemUuidMap::value_type>
+GetPlatformKeySystemUUIDMappings() {
+  return std::vector<
+      ::media::MediaClientAndroid::KeySystemUuidMap::value_type>();
+}
+#endif
+
 }  // namespace media
 }  // namespace chromecast