Android webview tries to switch to CE context

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;
@@ skipping 181 matching lines @@
      * Constructor called by the API 22 version of {@link WebViewFactory} and later.
      */
     public WebViewChromiumFactoryProvider(android.webkit.WebViewDelegate delegate) {
         initialize(WebViewDelegateFactory.createProxyDelegate(delegate));
     }
 
     @SuppressFBWarnings("DMI_HARDCODED_ABSOLUTE_FILENAME")
     private void initialize(WebViewDelegate webViewDelegate) {
         mWebViewDelegate = webViewDelegate;
 
-        checkStorageIsNotDeviceProtected(mWebViewDelegate.getApplication());
+        switchStorageContextIfDeviceProtectedStorage(mWebViewDelegate.getApplication());
 
         // WebView needs to make sure to always use the wrapped application context.
         ContextUtils.initApplicationContext(
                 ResourcesContextWrapperFactory.get(
                         mWebViewDelegate.getApplication().getApplicationContext()));
 
         if (isBuildDebuggable()) {
             // Suppress the StrictMode violation as this codepath is only hit on debuggable builds.
             StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
             CommandLine.initFromFile(COMMAND_LINE_FILE);
@@ skipping 33 matching lines @@
         }
         if (lastVersion != currentVersion) {
             mWebViewPrefs.edit().putInt(VERSION_CODE_PREF, currentVersion).apply();
         }
 
         mShouldDisableThreadChecking =
                 shouldDisableThreadChecking(ContextUtils.getApplicationContext());
         // Now safe to use WebView data directory.
     }
 
-    static void checkStorageIsNotDeviceProtected(Context context) {
+    static void switchStorageContextIfDeviceProtectedStorage(Context context) {
         if ((Build.VERSION.CODENAME.equals("N") || Build.VERSION.SDK_INT > Build.VERSION_CODES.M)
                 && context.isDeviceProtectedStorage()) {
-            throw new IllegalArgumentException(
-                    "WebView cannot be used with device protected storage");
+            // Try to switch to a CE-protected context
+            try {
+                context.createCredentialProtectedStorageContext();

[Torne, 2016/09/15 10:15:59]

This doesn't actually switch anything - you aren't using the return value, so
the credential-protected context is never used.

+            } catch (Exception e) {
+                throw new IllegalArgumentException(
+                        "WebView cannot be used with device protected storage");
+            }
         }
     }
 
     private static boolean isBuildDebuggable() {
         return !Build.TYPE.equals("user");
     }
 
     /**
      * Both versionCodes should be from a WebView provider package implemented by Chromium.
      * VersionCodes from other kinds of packages won't make any sense in this method.
@@ skipping 375 matching lines @@
                 mWebViewDatabase = new WebViewDatabaseAdapter(this, awDatabase);
             }
         }
         return mWebViewDatabase;
     }
 
     WebViewDelegate getWebViewDelegate() {
         return mWebViewDelegate;
     }
 }