[DO NOT MERGE] Rollup Cert-related changes from R

This change includes the following commits from internal R branch
which are related to certificate management:

0206e76f46 CredentialStorage: Install keys using KeyChain
09ceea53d9 Added functionality to select type of certificate to be installed from the Settings app
3acf3f5433 WiFi certificates installable from Wifi sub-preference
8439fd15f7 Fix strings for certificate installation in Settings

Bug: 161347472
Test: builds & manual testing
Change-Id: Ia59dc4780254fab4f34c2f61b25f3b4e56ed7b77

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

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2017 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.os.UserManager;
+
+public class InstallCertificatePreferenceController extends
+        RestrictedEncryptionPreferenceController {
+
+    private static final String KEY_INSTALL_CERTIFICATE = "install_certificate";
+
+    public InstallCertificatePreferenceController(Context context) {
+        super(context, UserManager.DISALLOW_CONFIG_CREDENTIALS);
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return KEY_INSTALL_CERTIFICATE;
+    }
+}