EME: Remove reference to "concrete" key systems.

media/base/key_systems.h

Index: media/base/key_systems.h
diff --git a/media/base/key_systems.h b/media/base/key_systems.h
index 1c9f8cc101570d72fe585b32aabd16939aa93999..92c15d899ad5a77ab55398b4f76d1b32c0cb771b 100644
--- a/media/base/key_systems.h
+++ b/media/base/key_systems.h
@@ -80,14 +80,13 @@ MEDIA_EXPORT bool IsSupportedKeySystemWithInitDataType(
 // Returns a name for |key_system| suitable to UMA logging.
 MEDIA_EXPORT std::string GetKeySystemNameForUMA(const std::string& key_system);
 
-// Returns whether AesDecryptor can be used for the given |concrete_key_system|.
-MEDIA_EXPORT bool CanUseAesDecryptor(const std::string& concrete_key_system);
+// Returns whether AesDecryptor can be used for the given |key_system|.
+MEDIA_EXPORT bool CanUseAesDecryptor(const std::string& key_system);
 
 #if defined(ENABLE_PEPPER_CDMS)
-// Returns the Pepper MIME type for |concrete_key_system|.
-// Returns empty string if |concrete_key_system| is unknown or not Pepper-based.
-MEDIA_EXPORT std::string GetPepperType(
-    const std::string& concrete_key_system);
+// Returns the Pepper MIME type for |key_system|.
+// Returns empty string if |key_system| is unknown or not Pepper-based.
+MEDIA_EXPORT std::string GetPepperType(const std::string& key_system);
 #endif
 
 #if defined(UNIT_TEST)