Fix unnecessarily non-static inner class to static inner

Change-Id: I0c8efda6ef0bede6b5871cd651f42db82dbfbd39
diff --git a/services/core/java/com/android/server/InputMethodManagerService.java b/services/core/java/com/android/server/InputMethodManagerService.java
index 74ae812..4687e3f 100644
--- a/services/core/java/com/android/server/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/InputMethodManagerService.java
@@ -204,7 +204,7 @@
     private boolean mNotificationShown;
     private final boolean mImeSelectedOnBoot;
 
-    class SessionState {
+    static class SessionState {
         final ClientState client;
         final IInputMethod method;