Unify IMEDriver and IMEServer.

services/ui/public/interfaces/ime/ime.mojom

Index: services/ui/public/interfaces/ime/ime.mojom
diff --git a/services/ui/public/interfaces/ime/ime.mojom b/services/ui/public/interfaces/ime/ime.mojom
index b38453e600db8587f8c46f9c851845169938a428..8251ac636656f528560698967060ebffc293b87f 100644
--- a/services/ui/public/interfaces/ime/ime.mojom
+++ b/services/ui/public/interfaces/ime/ime.mojom
@@ -130,15 +130,6 @@ struct StartSessionDetails {
 // the client via the InputMethod interface, and sends composition events to
 // the client via the TextInputClient.
 interface IMEDriver {
-  // session_id is unique and generated by Mus.
-  StartSession(int32 session_id, StartSessionDetails details);
-  CancelSession(int32 session_id);
-};
-
-// Clients use IME using the IMEServer interface which is provided by Mus. Mus
-// does minimal processing and mostly just acts as lightweight proxy between
-// the client app and the registered IME driver.
-interface IMEServer {
   StartSession(StartSessionDetails details);
 };