Get FragmentManager directly from AccountSigninView.Delegate.

chrome/android/java/src/org/chromium/chrome/browser/signin/AccountSigninView.java

 // Copyright 2015 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.signin;
 
 import android.app.Activity;
+import android.app.FragmentManager;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.text.TextUtils;
 import android.text.method.LinkMovementMethod;
 import android.util.AttributeSet;
 import android.view.View;
 import android.widget.Button;
 import android.widget.FrameLayout;
 import android.widget.ImageView;
 import android.widget.TextView;
@@ skipping 56 matching lines @@
         public void onFailedToSetForcedAccount(String forcedAccountName);
     }
 
     // TODO(peconn): Investigate expanding the Delegate to simplify the Listener implementations.
 
     /**
      * Provides UI objects for new UI component creation.
      */
     public interface Delegate {
         /**
-         * Provides an Activity for the view to create dialogs.
+         * Provides an Activity for the View to check GMSCore version.
          */
         public Activity getActivity();
+
+        /**
+         * Provides a FragmentManager for the View to create dialogs. This is done through a
+         * different mechanism than getActivity().getFragmentManager() as a potential fix to
+         * https://crbug.com/646978 on the theory that getActivity() and getFragmentManager()
+         * return null at different times.
+         */
+        public FragmentManager getFragmentManager();
     }
 
     private static final String TAG = "AccountSigninView";
 
     private static final String SETTINGS_LINK_OPEN = "<LINK1>";
     private static final String SETTINGS_LINK_CLOSE = "</LINK1>";
 
     private AccountManagerHelper mAccountManagerHelper;
     private List<String> mAccountNames;
     private AccountSigninChooseView mSigninChooseView;
@@ skipping 152 matching lines @@
 
         mProfileData.update();
 
         // Determine how the accounts have changed. Each list should only have unique elements.
         if (oldAccountNames == null || oldAccountNames.isEmpty()) return;
 
         if (!mAccountNames.get(accountToSelect).equals(oldAccountNames.get(oldSelectedAccount))) {
             // Any dialogs that may have been showing are now invalid (they were created for the
             // previously selected account).
             ConfirmSyncDataStateMachine
-                    .cancelAllDialogs(mDelegate.getActivity().getFragmentManager());
+                    .cancelAllDialogs(mDelegate.getFragmentManager());
 
             if (mAccountNames.containsAll(oldAccountNames)) {
                 // A new account has been added and no accounts have been deleted. We will have
                 // changed the account selection to the newly added account, so shortcut to the
                 // confirm signin page.
                 showConfirmSigninPageAccountTrackerServiceCheck();
             }
         }
     }
 
@@ skipping 109 matching lines @@
                         @Override
                         public void onSystemAccountsChanged() {}
                     });
         }
     }
 
     private void showConfirmSigninPagePreviousAccountCheck() {
         String accountName = getSelectedAccountName();
         ConfirmSyncDataStateMachine.run(PrefServiceBridge.getInstance().getSyncLastAccountName(),
                 accountName, ImportSyncType.PREVIOUS_DATA_FOUND,
-                mDelegate.getActivity().getFragmentManager(),
+                mDelegate.getFragmentManager(),
                 getContext(), new ConfirmImportSyncDataDialog.Listener() {
                     @Override
                     public void onConfirm(boolean wipeData) {
                         SigninManager.wipeSyncUserDataIfRequired(wipeData)
                                 .then(new Callback<Void>() {
                                     @Override
                                     public void onResult(Void v) {
                                         showConfirmSigninPage();
                                     }
                                 });
@@ skipping 137 matching lines @@
      * @return Whether the view is in "no choice, just a confirmation" forced-account mode.
      */
     public boolean isInForcedAccountMode() {
         return mForcedAccountName != null;
     }
 
     private String getSelectedAccountName() {
         return mAccountNames.get(mSigninChooseView.getSelectedAccountPosition());
     }
 }