Fix another source of flakiness in ErrorPageTest

chrome/test/automation/tab_proxy.cc

 // Copyright (c) 2006-2008 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.
 
 #include "chrome/test/automation/tab_proxy.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "chrome/common/json_value_serializer.h"
@@ skipping 142 matching lines @@
 bool TabProxy::NeedsAuth() const {
   if (!is_valid())
     return false;
 
   bool needs_auth = false;
   sender_->Send(new AutomationMsg_NeedsAuth(0, handle_, &needs_auth));
   return needs_auth;
 }
 
 AutomationMsg_NavigationResponseValues TabProxy::GoBack() {
+  return GoBackBlockUntilNavigationsComplete(1);
+}
+
+AutomationMsg_NavigationResponseValues
+    TabProxy::GoBackBlockUntilNavigationsComplete(int number_of_navigations) {
   if (!is_valid())
     return AUTOMATION_MSG_NAVIGATION_ERROR;
 
   AutomationMsg_NavigationResponseValues navigate_response =
       AUTOMATION_MSG_NAVIGATION_ERROR;
-  sender_->Send(new AutomationMsg_GoBack(0, handle_, &navigate_response));
+  sender_->Send(new AutomationMsg_GoBackBlockUntilNavigationsComplete(
+      0, handle_, number_of_navigations, &navigate_response));
   return navigate_response;
 }
 
 AutomationMsg_NavigationResponseValues TabProxy::GoForward() {
+  return GoForwardBlockUntilNavigationsComplete(1);
+}
+
+AutomationMsg_NavigationResponseValues
+    TabProxy::GoForwardBlockUntilNavigationsComplete(
+        int number_of_navigations) {
   if (!is_valid())
     return AUTOMATION_MSG_NAVIGATION_ERROR;
 
   AutomationMsg_NavigationResponseValues navigate_response =
       AUTOMATION_MSG_NAVIGATION_ERROR;
-  sender_->Send(new AutomationMsg_GoForward(0, handle_, &navigate_response));
+  sender_->Send(new AutomationMsg_GoForwardBlockUntilNavigationsComplete(
+      0, handle_, number_of_navigations, &navigate_response));
   return navigate_response;
 }
 
 AutomationMsg_NavigationResponseValues TabProxy::Reload() {
   if (!is_valid())
     return AUTOMATION_MSG_NAVIGATION_ERROR;
 
   AutomationMsg_NavigationResponseValues navigate_response =
       AUTOMATION_MSG_NAVIGATION_ERROR;
   sender_->Send(new AutomationMsg_Reload(0, handle_, &navigate_response));
@@ skipping 520 matching lines @@
   AutoLock lock(list_lock_);
   observers_list_.RemoveObserver(observer);
 }
 
 // Called on Channel background thread, if TabMessages filter is installed.
 void TabProxy::OnMessageReceived(const IPC::Message& message) {
   AutoLock lock(list_lock_);
   FOR_EACH_OBSERVER(TabProxyDelegate, observers_list_,
                     OnMessageReceived(this, message));
 }