Query right user's system IMEs in AppRestrictionsHelper

It turns out that AppRestrictionsHelper#addSystemImes() has always
queried for the owner user's system IMEs despite the fact that it's
trying to query system IMEs for a restricted profile user.  This
behavior has not changed since its beginning [1].

Most likely people would not have noticed this though, because:

* Settings app does not show a menu item to create a restricted user
   on phone devices.
 * Even if it's available, most people do not use restricted users.
 * Even if someone created a restrected user, most likely the owner
   user and the restrected user share the same set of system IMEs,
   which are defined as "pre-installed" IMEs.

Anyway, AppRestrictionsHelper#addSystemImes() will start using a newly
introduced @hide API IMM#getEnabledInputMethodListAsUser() so that it
can query for the right user's system IMEs, instead of querying owner
user's ones.

 [1]: Ifced841ad3bfbde33d2403356216dd1749b7fa9a
      a7a93784d1f9798d37cb618def1a558f8d626f0f

Bug: 122164939
Test: atest SettingsLibTests:AppRestrictionsHelperTest
Test: manually done as follows.
  1. Build aosp_taimen-userdebug and flash it.
  2. adb shell pm create-user --restricted test_profile
  3. adb shell am start -a android.settings.USER_SETTINGS
  4. Click the gear icon next to the "test_profile" user.
  5. By adding a log, make sure that IMMS#getInputMethodList()
     gets called with userId = 10.
Change-Id: I5b50b5fe143c74c87b331bda3e5bcc4d6248436e

core/java/android/view/inputmethod/InputMethodManager.java

@@ -966,7 +966,26 @@ public final class InputMethodManager {
      */
     public List<InputMethodInfo> getInputMethodList() {
         try {
-            return mService.getInputMethodList();
+            // We intentionally do not use UserHandle.getCallingUserId() here because for system
+            // services InputMethodManagerInternal.getInputMethodListAsUser() should be used
+            // instead.
+            return mService.getInputMethodList(UserHandle.myUserId());
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Returns the list of installed input methods for the specified user.
+     *
+     * @param userId user ID to query
+     * @return {@link List} of {@link InputMethodInfo}.
+     * @hide
+     */
+    @RequiresPermission(INTERACT_ACROSS_USERS_FULL)
+    public List<InputMethodInfo> getInputMethodListAsUser(@UserIdInt int userId) {
+        try {
+            return mService.getInputMethodList(userId);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }

core/java/com/android/internal/view/IInputMethodManager.aidl

@@ -34,7 +34,7 @@ interface IInputMethodManager {
             int untrustedDisplayId);
 
     // TODO: Use ParceledListSlice instead
-    List<InputMethodInfo> getInputMethodList();
+    List<InputMethodInfo> getInputMethodList(int userId);
     // TODO: Use ParceledListSlice instead
     List<InputMethodInfo> getEnabledInputMethodList(int userId);
     List<InputMethodSubtype> getEnabledInputMethodSubtypeList(in String imiId,

packages/SettingsLib/src/com/android/settingslib/users/AppRestrictionsHelper.java

@@ -420,7 +420,7 @@ public class AppRestrictionsHelper {
         List<InputMethodInfo> getInputMethodList() {
             InputMethodManager imm = (InputMethodManager) getContext().getSystemService(
                     Context.INPUT_METHOD_SERVICE);
-            return imm.getInputMethodList();
+            return imm.getInputMethodListAsUser(mUser.getIdentifier());
         }
     }
 }

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

@@ -1627,10 +1627,12 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
     }
 
     @Override
-    public List<InputMethodInfo> getInputMethodList() {
-        final int callingUserId = UserHandle.getCallingUserId();
+    public List<InputMethodInfo> getInputMethodList(@UserIdInt int userId) {
+        if (UserHandle.getCallingUserId() != userId) {
+            mContext.enforceCallingPermission(Manifest.permission.INTERACT_ACROSS_USERS_FULL, null);
+        }
         synchronized (mMethodMap) {
-            final int[] resolvedUserIds = InputMethodUtils.resolveUserId(callingUserId,
+            final int[] resolvedUserIds = InputMethodUtils.resolveUserId(userId,
                     mSettings.getCurrentUserId(), null);
             if (resolvedUserIds.length != 1) {
                 return Collections.emptyList();

services/core/java/com/android/server/inputmethod/MultiClientInputMethodManagerService.java

@@ -1236,8 +1236,11 @@ public final class MultiClientInputMethodManagerService {
 
         @BinderThread
         @Override
-        public List<InputMethodInfo> getInputMethodList() {
-            return mInputMethodInfoMap.getAsList(UserHandle.getUserId(Binder.getCallingUid()));
+        public List<InputMethodInfo> getInputMethodList(@UserIdInt int userId) {
+            if (UserHandle.getCallingUserId() != userId) {
+                mContext.enforceCallingPermission(INTERACT_ACROSS_USERS_FULL, null);
+            }
+            return mInputMethodInfoMap.getAsList(userId);
         }
 
         @BinderThread