Allow disk writes while checking webview version pref.

android_webview/glue/java/src/com/android/webview/chromium/WebViewChromiumFactoryProvider.java

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package com.android.webview.chromium;
 
 import android.Manifest;
 import android.app.ActivityManager;
 import android.content.ComponentCallbacks2;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.net.Uri;
 import android.os.Build;
 import android.os.Looper;
 import android.os.Process;
+import android.os.StrictMode;
 import android.os.UserManager;
 import android.provider.Settings;
 import android.util.Log;
 import android.webkit.CookieManager;
 import android.webkit.GeolocationPermissions;
 import android.webkit.ServiceWorkerController;
 import android.webkit.TokenBindingService;
 import android.webkit.ValueCallback;
 import android.webkit.WebStorage;
 import android.webkit.WebView;
@@ skipping 212 matching lines @@
         ThreadUtils.setWillOverrideUiThread();
         // Load chromium library.
         AwBrowserProcess.loadLibrary();
 
         final PackageInfo packageInfo = WebViewFactory.getLoadedPackageInfo();
 
         // Load glue-layer support library.
         System.loadLibrary("webviewchromium_plat_support");
 
         // Use shared preference to check for package downgrade.
-        mWebViewPrefs = ContextUtils.getApplicationContext().getSharedPreferences(
-                CHROMIUM_PREFS_NAME, Context.MODE_PRIVATE);
+        // Since N, getSharedPreferences creates the preference dir if it doesn't exist,
+        // causing a disk write.
+        StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskWrites();
+        try {
+            mWebViewPrefs = ContextUtils.getApplicationContext().getSharedPreferences(
+                    CHROMIUM_PREFS_NAME, Context.MODE_PRIVATE);
+        } finally {
+            StrictMode.setThreadPolicy(oldPolicy);
+        }
         int lastVersion = mWebViewPrefs.getInt(VERSION_CODE_PREF, 0);
         int currentVersion = packageInfo.versionCode;
         if (!versionCodeGE(currentVersion, lastVersion)) {
             // The WebView package has been downgraded since we last ran in this application.
             // Delete the WebView data directory's contents.
             String dataDir = PathUtils.getDataDirectory();
             Log.i(TAG, "WebView package downgraded from " + lastVersion + " to " + currentVersion
                             + "; deleting contents of " + dataDir);
             deleteContents(new File(dataDir));
         }
@@ skipping 431 matching lines @@
     WebViewDelegate getWebViewDelegate() {
         return mWebViewDelegate;
     }
 
     // The method to support unreleased Android.
     WebViewContentsClientAdapter createWebViewContentsClientAdapter(WebView webView,
             Context context) {
         return new WebViewContentsClientAdapter(webView, context, mWebViewDelegate);
     }
 }