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

components/cdm/renderer/widevine_key_systems.h

Index: components/cdm/renderer/widevine_key_systems.h
diff --git a/components/cdm/renderer/widevine_key_systems.h b/components/cdm/renderer/widevine_key_systems.h
index 3bed60ca4a601fc272b5325929020d7c1b431818..ab1966f03a86218abea1d5f3572bc395da411a7b 100644
--- a/components/cdm/renderer/widevine_key_systems.h
+++ b/components/cdm/renderer/widevine_key_systems.h
@@ -23,11 +23,6 @@ void AddWidevineWithCodecs(
     content::SupportedCodecs supported_codecs,
     std::vector<content::KeySystemInfo>* concrete_key_systems);
 
-#if defined(OS_ANDROID)
-void AddAndroidWidevine(
-    std::vector<content::KeySystemInfo>* concrete_key_systems);
-#endif  // defined(OS_ANDROID)
-
 }  // namespace cdm
 
 #endif  // COMPONENTS_CDM_RENDERER_WIDEVINE_KEY_SYSTEMS_H_