[ChromeDriver] Select the main frame if a non-existant child frame is targeted.

chrome/test/chromedriver/session.cc

 // Copyright (c) 2012 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/chromedriver/session.h"
 
 #include "chrome/test/chromedriver/chrome.h"
+#include "chrome/test/chromedriver/status.h"
 
 Session::Session(const std::string& id)
     : id(id), mouse_position(0, 0), implicit_wait(0), page_load_timeout(0),
       script_timeout(0) {}
 
 Session::Session(const std::string& id, scoped_ptr<Chrome> chrome)
     : id(id), chrome(chrome.Pass()), mouse_position(0, 0), implicit_wait(0),
       page_load_timeout(0), script_timeout(0) {}
 
 Session::~Session() {}
 
+Status Session::WaitForPendingNavigations() {
+  if (!chrome)
+    return Status(kOk);
+  std::string full_frame_id(frame);
+  if (full_frame_id == "") {
+    Status status = chrome->GetMainFrame(&full_frame_id);
+    if (status.IsError())
+      return status;
+  }
+  return chrome->WaitForPendingNavigations(full_frame_id);
+}
+
 SessionAccessorImpl::SessionAccessorImpl(scoped_ptr<Session> session)
     : session_(session.Pass()) {}
 
 Session* SessionAccessorImpl::Access(scoped_ptr<base::AutoLock>* lock) {
   lock->reset(new base::AutoLock(session_lock_));
   return session_.get();
 }
 
 SessionAccessorImpl::~SessionAccessorImpl() {}