Update WebView implementation Dev Setting - new looks + descriptions.

Now that we are changing the WebView package mechanism so that a package
can only be used as WebView implementation if that package is enabled
for all users of the device we need to tell the user why a package can't
be chosen as WebView implementation.
With this CL we do so in the 'Set WebView Implementation' Developer
Setting.

We code for the WebView implementation Developer Setting is now based on
the same code as that of the Debug App Developer Setting.

Bug: 32894154
Test: Ensure WebView Implementation setting shows correct packages.
Test: Ensure WebView Implementation setting shows correct descriptions
for why a package is not usable - including the case where packages are
disabled/uninstalled for a second user.
Test: Ensure the summary for the WebView Implmentation setting is
updated after changing WebView package.
Test: Ensure the WebView package Activity
(Settings.ACTION_WEBVIEW_SETTINGS) is similar to the Dev Setting.
Test: ensure non-admin user cannot start WV-picker activity through
'adb shell am start -n com.android.settings/.WebViewImplementation'

Change-Id: Ia6e6e9e12ce8f8f45ec539807cd0c6479acb8ecb

src/com/android/settings/webview/WebViewAppPreferenceController.java

@@ -0,0 +1,103 @@
+/*
+ * 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.webview;
+
+import android.app.Activity;
+import android.content.pm.PackageInfo;
+import android.content.Context;
+import android.content.Intent;
+import android.support.annotation.VisibleForTesting;
+import android.support.v7.preference.Preference;
+import android.support.v7.preference.PreferenceScreen;
+
+import com.android.settings.DevelopmentSettings;
+import com.android.settings.core.PreferenceController;
+
+public class WebViewAppPreferenceController extends PreferenceController {
+
+    private static final String WEBVIEW_APP_KEY = "select_webview_provider";
+
+    private Context mContext;
+    private Preference mPreference;
+    private final WebViewUpdateServiceWrapper mWebViewUpdateServiceWrapper;
+
+    public WebViewAppPreferenceController(Context context) {
+        this(context, new WebViewUpdateServiceWrapper());
+    }
+
+    public WebViewAppPreferenceController(Context context,
+            WebViewUpdateServiceWrapper webviewUpdateServiceWrapper) {
+        super(context);
+        mContext = context;
+        mWebViewUpdateServiceWrapper = webviewUpdateServiceWrapper;
+    }
+
+    @Override
+    public boolean handlePreferenceTreeClick(Preference preference) {
+        if (getPreferenceKey().equals(preference.getKey())) {
+            return true;
+        }
+        return false;
+    }
+
+    public Intent getActivityIntent() {
+        return new Intent(mContext, WebViewAppPicker.class);
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        mPreference.setSummary(getCurrentWebViewPackageLabel(mContext));
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        if (isAvailable()) {
+            mPreference = screen.findPreference(WEBVIEW_APP_KEY);
+        }
+    }
+
+    /**
+     * Handle the return-value from the WebViewAppPicker Activity.
+     */
+    public void onActivityResult(int resultCode, Intent data) {
+        if (resultCode == Activity.RESULT_OK) {
+            updateState(null);
+        }
+    }
+
+    private String getCurrentWebViewPackageLabel(Context context) {
+        PackageInfo webViewPackage = mWebViewUpdateServiceWrapper.getCurrentWebViewPackage();
+        if (webViewPackage == null) return "";
+        return webViewPackage.applicationInfo.loadLabel(context.getPackageManager()).toString();
+    }
+
+
+    @Override
+    public String getPreferenceKey() {
+        return WEBVIEW_APP_KEY;
+    }
+
+    @Override
+    public boolean isAvailable() {
+        return true;
+    }
+
+    public void enablePreference(boolean enabled) {
+        if (isAvailable()) {
+            mPreference.setEnabled(enabled);
+        }
+    }
+}