Add an IPC to return the platform supported key-system names in Android.

media/base/android/media_drm_bridge.cc

Index: media/base/android/media_drm_bridge.cc
diff --git a/media/base/android/media_drm_bridge.cc b/media/base/android/media_drm_bridge.cc
index fc0288ab77381376ccbce06caf3035d0f1fe86ca..60215ea6148437cab339d3e67cb287443f3b2ed8 100644
--- a/media/base/android/media_drm_bridge.cc
+++ b/media/base/android/media_drm_bridge.cc
@@ -73,6 +73,7 @@ class KeySystemUuidManager {
   KeySystemUuidManager();
   UUID GetUUID(const std::string& key_system);
   void AddMapping(const std::string& key_system, const UUID& uuid);
+  std::vector<std::string> GetPlatformKeySystemNames();
 
  private:
   typedef base::hash_map<std::string, UUID> KeySystemUuidMap;
@@ -105,6 +106,17 @@ void KeySystemUuidManager::AddMapping(const std::string& key_system,
   key_system_uuid_map_[key_system] = uuid;
 }
 
+std::vector<std::string> KeySystemUuidManager::GetPlatformKeySystemNames() {
+  std::vector<std::string> key_systems;
+  for (KeySystemUuidMap::iterator it = key_system_uuid_map_.begin();
+       it != key_system_uuid_map_.end(); ++it) {
+    // Rule out the key system handled by Chrome explicitly.
+    if (it->first != kWidevineKeySystem)
+      key_systems.push_back(it->first);
+  }
+  return key_systems;
+}
+
 base::LazyInstance<KeySystemUuidManager>::Leaky g_key_system_uuid_manager =
     LAZY_INSTANCE_INITIALIZER;
 
@@ -264,13 +276,18 @@ bool MediaDrmBridge::IsSecurityLevelSupported(const std::string& key_system,
   return media_drm_bridge->SetSecurityLevel(security_level);
 }
 
-//static
+// static
 void MediaDrmBridge::AddKeySystemUuidMapping(const std::string& key_system,
                                              const std::vector<uint8>& uuid) {
   g_key_system_uuid_manager.Get().AddMapping(key_system, uuid);
 }
 
 // static
+std::vector<std::string> MediaDrmBridge::GetPlatformKeySystemNames() {
+  return g_key_system_uuid_manager.Get().GetPlatformKeySystemNames();
+}
+
+// static
 bool MediaDrmBridge::IsKeySystemSupported(const std::string& key_system) {
   DCHECK(!key_system.empty());
   return IsKeySystemSupportedWithTypeImpl(key_system, "");