Add promise type to EME idl files

Source/modules/encryptedmedia/MediaKeySession.idl

Index: Source/modules/encryptedmedia/MediaKeySession.idl
diff --git a/Source/modules/encryptedmedia/MediaKeySession.idl b/Source/modules/encryptedmedia/MediaKeySession.idl
index d81309d6d6085adb4521cc6f3a311a69d7d2b53a..c0c5035f1d21aa75b964018ff5615221c68e9131 100644
--- a/Source/modules/encryptedmedia/MediaKeySession.idl
+++ b/Source/modules/encryptedmedia/MediaKeySession.idl
@@ -39,13 +39,13 @@
     [CallWith=ScriptState] readonly attribute Promise closed;
 
     // session initialization
-    [CallWith=ScriptState] Promise generateRequest(DOMString initDataType, ArrayBuffer initData);
-    [CallWith=ScriptState] Promise generateRequest(DOMString initDataType, ArrayBufferView initData);
-    [CallWith=ScriptState] Promise load(DOMString sessionId);
+    [CallWith=ScriptState] Promise<void> generateRequest(DOMString initDataType, ArrayBuffer initData);
+    [CallWith=ScriptState] Promise<void> generateRequest(DOMString initDataType, ArrayBufferView initData);
+    [CallWith=ScriptState] Promise<boolean> load(DOMString sessionId);
 
     // session operations
-    [CallWith=ScriptState] Promise update(ArrayBuffer response);
-    [CallWith=ScriptState] Promise update(ArrayBufferView response);
-    [CallWith=ScriptState] Promise close();
-    [CallWith=ScriptState] Promise remove();
+    [CallWith=ScriptState] Promise<void> update(ArrayBuffer response);
+    [CallWith=ScriptState] Promise<void> update(ArrayBufferView response);
+    [CallWith=ScriptState] Promise<void> close();
+    [CallWith=ScriptState] Promise<void> remove();
 };