[Webview, Child Accounts] Automatically sign in to Chrome if needed.

chrome/android/java/src/org/chromium/chrome/browser/childaccounts/ChildAccountService.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 org.chromium.chrome.browser.childaccounts;
 
 import android.accounts.Account;
 import android.content.Context;
 
 import org.chromium.base.Callback;
 import org.chromium.base.ThreadUtils;
+import org.chromium.base.annotations.CalledByNative;
 import org.chromium.components.signin.AccountManagerHelper;
 
 /**
- * This class serves as a simple interface for querying the child account information.
- * It has two methods namely, checkHasChildAccount(...) which is asynchronous and queries the
- * system directly for the information and the synchronous isChildAccount() which asks the native
- * side assuming it has been set correctly already.
+ * This class serves as a simple interface for querying the child account information. It has two
+ * methods for querying the child account information; checkHasChildAccount(...) which is
+ * asynchronous and queries the system directly for the information and the synchronous
+ * isChildAccount() which asks the native side assuming it has been set correctly already.
  *
  * The former method is used by ForcedSigninProcessor and FirstRunFlowSequencer to detect child
- * accounts since the native side is only activated on signing in.
- * Once signed in by the ForcedSigninProcessor, the ChildAccountInfoFetcher will notify the native
- * side and also takes responsibility for monitoring changes and taking a suitable action.
+ * accounts since the native side is only activated on signing in. Once signed in by the
+ * ForcedSigninProcessor, the ChildAccountInfoFetcher will notify the native side and also takes
+ * responsibility for monitoring changes and taking a suitable action.
+ *
+ * The class also provides an interface through which a client can listen for child account status
+ * changes. When the SupervisedUserContentProvider forces sign-in it waits for a status change
+ * before querying the URL filters.
  */
 public class ChildAccountService {
     private ChildAccountService() {
         // Only for static usage.
     }
 
     /**
      * Checks for the presence of child accounts on the device.
      *
      * @param callback A callback which will be called with the result.
@@ skipping 16 matching lines @@
     /**
      * Returns the previously determined value of whether there is a child account on the device.
      * Should only be called after the native library and profile have been loaded.
      *
      * @return The previously determined value of whether there is a child account on the device.
      */
     public static boolean isChildAccount() {
         return nativeIsChildAccount();
     }
 
+    public static void listenForStatusChange(Runnable callback) {

[Bernhard Bauer, 2017/02/15 15:09:37]

Javadoc for public methods. In particular, when and how often is the callback
going to be called?

You could also have this method take a Callback<Boolean> which gets the child
account status, which would have the additional advantage that you can directly
call run() on the Callback from C++ without having to go through an additional
method here.

[aberent, 2017/02/15 18:34:46]

Done.

+        nativeListenForChildStatusReceived(callback);
+    }
+
+    @CalledByNative
+    private static void childStatusReceived(Runnable callback) {
+        callback.run();
+    }
+
     private static native boolean nativeIsChildAccount();
+
+    private static native void nativeListenForChildStatusReceived(Runnable callback);
 }