Adds MediaClientAndroid to support embedder/MediaDrmBridge interaction.

chromecast/media/base/key_systems_common.h

Index: chromecast/media/base/key_systems_common.h
diff --git a/chromecast/media/base/key_systems_common.h b/chromecast/media/base/key_systems_common.h
index 4ab8ea75dec72e93fe5252551e6aa4592c02f0d7..a6b78fa5679021f2d7c4e4d0336e51076e6dd534 100644
--- a/chromecast/media/base/key_systems_common.h
+++ b/chromecast/media/base/key_systems_common.h
@@ -6,6 +6,10 @@
 #define CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_
 
 #include <string>
+#include <utility>
+#include <vector>
+
+#include "base/compiler_specific.h"
 
 namespace chromecast {
 namespace media {
@@ -29,6 +33,13 @@ CastKeySystem GetKeySystemByName(const std::string& key_system_name);
 // TODO(gunsch): Remove when prefixed EME is removed.
 CastKeySystem GetPlatformKeySystemByName(const std::string& key_system_name);
 
+// Translates a platform-specific key system string into a CastKeySystem.
+// TODO(gunsch): Remove when prefixed EME is removed.
+#if defined(OS_ANDROID)
+std::vector<std::pair<std::string, std::vector<uint8_t>>>
+GetPlatformKeySystemUUIDMappings();
+#endif
+
 }  // namespace media
 }  // namespace chromecast