Simplify IMMS#startVrInputMethodNoCheck a bit

This is a follow up CL to a recent CL [1] that added VR-IME support.

Currently, IMMS#startVrInputMethodNoCheck() internally calls
IMMS#setInputMethodEnabled(), which enforces the caller user ID check
and caller permission check for WRITE_SECURE_SETTINGS.

This appears to make sense for IMMS#startVrInputMethodNoCheck(), but
in reallity IMMS#startVrInputMethodNoCheck() always gets called on
non-binder system server thread hence those checks will never fail.

Note that such a call path is fine and not a security issue.  What this
CL tries to address is just replace IMMS#setInputMethodEnabledLocked()
to make it clear that IMMS allows such an operation for callers that
have RESTRICTED_VR_ACCESS is intentional.

To summarize, this CL just removes redundant operations and there
should be no visible behavior change.

 [1]: I1db7981b5198e7e203d4578cae7e5b6d20037d0d
      89a6c48a8b

Bug: 63037786
Test: compile
Change-Id: Iec43177bd698de6efa453d64ceafec3164538151

services/core/java/com/android/server/InputMethodManagerService.java

@@ -889,7 +889,7 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
 
     /**
      * Start a VR InputMethod that matches IME with package name of {@param component}.
-     * Note: This method is called from {@link VrManager}.
+     * Note: This method is called from {@link android.app.VrManager}.
      */
     private void startVrInputMethodNoCheck(@Nullable ComponentName component) {
         if (component == null) {
@@ -903,7 +903,7 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
             for (InputMethodInfo info : mMethodList) {
                 if (TextUtils.equals(info.getPackageName(), packageName) && info.isVrOnly()) {
                     // set this is as current inputMethod without updating settings.
-                    setInputMethodEnabled(info.getId(), true);
+                    setInputMethodEnabledLocked(info.getId(), true);
                     setInputMethodLocked(info.getId(), NOT_A_SUBTYPE_ID);
                     break;
                 }