Disentangle input manager service startup.

We will be adding additional callbacks for other components.
This change makes it clearer how the input manager is started
and where the callbacks are initialized.

Bug: 6548391
Change-Id: I4b2a61482126a12b7cf11fafe513f846c76c11e5
diff --git a/services/java/com/android/server/wm/InputMonitor.java b/services/java/com/android/server/wm/InputMonitor.java
index aa18ee4..61310ca 100644
--- a/services/java/com/android/server/wm/InputMonitor.java
+++ b/services/java/com/android/server/wm/InputMonitor.java
@@ -33,7 +33,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 
-final class InputMonitor implements InputManagerService.Callbacks {
+final class InputMonitor implements InputManagerService.WindowManagerCallbacks {
     private final WindowManagerService mService;
     
     // Current window with input focus for keys and other non-touch events.  May be null.