Add credential management app preference to Settings

Background
* This is part of the work to support
  a credential management app on
  unmanaged devices.
Changes
* Add a preference controller which will only
  be enabled if there is a credential management app.
* Add a fragment to display details on the credential
  management app and its policy. Add a remove button
  to remove the credential management app.
* Link CredentialManagementAppAdapter to new fragment
  and add expander.

Manual Testing
* Verify preference is disabled if there is no credential
  management app.
* Verify preference summary shows credential mangement
  app name if a credential management app exists.
* Verify fragment details page displays the
  authentication policy correctly.

Bug: 165641221
Test: Manual testing
      make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.security.CredentialManagementAppFragmentTest
      make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.security.CredentialManagementAppControllerTest
Change-Id: I06d6b88d0c89022f7a6cbf3031834defcb54bd51

src/com/android/settings/security/CredentialManagementAppPreferenceController.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.security;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.RemoteException;
+import android.security.IKeyChainService;
+import android.security.KeyChain;
+import android.util.Log;
+
+import androidx.preference.Preference;
+
+import com.android.settings.R;
+import com.android.settings.core.BasePreferenceController;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+/**
+ * Controller that shows and updates the credential management app summary.
+ */
+public class CredentialManagementAppPreferenceController extends BasePreferenceController {
+
+    private static final String TAG = "CredentialManagementApp";
+
+    private final ExecutorService mExecutor = Executors.newSingleThreadExecutor();
+    private final Handler mHandler = new Handler(Looper.getMainLooper());
+
+    private final PackageManager mPackageManager;
+    private boolean mHasCredentialManagerPackage;
+    private String mCredentialManagerPackageName;
+
+    public CredentialManagementAppPreferenceController(Context context, String key) {
+        super(context, key);
+        mPackageManager = context.getPackageManager();
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AVAILABLE;
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        mExecutor.execute(() -> {
+            try {
+                IKeyChainService service = KeyChain.bind(mContext).getService();
+                mHasCredentialManagerPackage = service.hasCredentialManagementApp();
+                mCredentialManagerPackageName = service.getCredentialManagementAppPackageName();
+            } catch (InterruptedException | RemoteException e) {
+                Log.e(TAG, "Unable to display credential management app preference");
+            }
+            mHandler.post(() -> displayPreference(preference));
+        });
+    }
+
+    private void displayPreference(Preference preference) {
+        if (mHasCredentialManagerPackage) {
+            preference.setEnabled(true);
+            try {
+                ApplicationInfo applicationInfo =
+                        mPackageManager.getApplicationInfo(mCredentialManagerPackageName, 0);
+                preference.setSummary(applicationInfo.loadLabel(mPackageManager));
+            } catch (PackageManager.NameNotFoundException e) {
+                preference.setSummary(mCredentialManagerPackageName);
+            }
+        } else {
+            preference.setEnabled(false);
+            preference.setSummary(R.string.no_certificate_management_app);
+        }
+    }
+}