Correctly handle FindNext from the Find dialog.

chrome_frame/chrome_frame_automation.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_frame/chrome_frame_automation.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/command_line.h"
@@ skipping 765 matching lines @@
     AutomationMsg_NavigationResponseValues result) {
   if (result == AUTOMATION_MSG_NAVIGATION_ERROR)
      ReportNavigationError(AUTOMATION_MSG_NAVIGATION_ERROR,
                            chrome_launch_params_->url().spec());
 }
 
 void ChromeFrameAutomationClient::FindInPage(const std::wstring& search_string,
                                              FindInPageDirection forward,
                                              FindInPageCase match_case,
                                              bool find_next) {
-  DCHECK(tab_.get());
+  // Note that we can be called by the find dialog after the tab has gone away.
+  if (!tab_)
+    return;
 
   // What follows is quite similar to TabProxy::FindInPage() but uses
   // the SyncMessageReplyDispatcher to avoid concerns about blocking
   // synchronous messages.
   AutomationMsg_Find_Params params;
   params.search_string = WideToUTF16Hack(search_string);
   params.find_next = find_next;
   params.match_case = (match_case == CASE_SENSITIVE);
   params.forward = (forward == FWD);
 
@@ skipping 525 matching lines @@
     const net::URLRequestStatus& status) {
   automation_server_->Send(new AutomationMsg_RequestEnd(
       tab_->handle(), request_id, status));
 }
 
 void ChromeFrameAutomationClient::OnCookiesRetrieved(bool success,
     const GURL& url, const std::string& cookie_string, int cookie_id) {
   automation_server_->Send(new AutomationMsg_GetCookiesHostResponse(
       tab_->handle(), success, url, cookie_string, cookie_id));
 }