Fix crashes in DownloadRequestLimiter when extension popups/bubbles initiate downloads automatically

chrome/browser/ui/tab_contents/tab_contents_wrapper.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/browser/ui/tab_contents/tab_contents_wrapper.h"
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "chrome/browser/autocomplete_history_manager.h"
 #include "chrome/browser/autofill/autofill_external_delegate.h"
 #include "chrome/browser/autofill/autofill_manager.h"
 #include "chrome/browser/automation/automation_tab_helper.h"
 #include "chrome/browser/content_settings/tab_specific_content_settings.h"
-#include "chrome/browser/download/download_request_limiter_observer.h"
 #include "chrome/browser/extensions/api/web_navigation/web_navigation_api.h"
 #include "chrome/browser/extensions/extension_tab_helper.h"
 #include "chrome/browser/external_protocol/external_protocol_observer.h"
 #include "chrome/browser/favicon/favicon_tab_helper.h"
 #include "chrome/browser/history/history_tab_helper.h"
 #include "chrome/browser/infobars/infobar_tab_helper.h"
 #include "chrome/browser/omnibox_search_hint.h"
 #include "chrome/browser/password_manager/password_manager.h"
 #include "chrome/browser/password_manager_delegate_impl.h"
 #include "chrome/browser/plugin_observer.h"
@@ skipping 88 matching lines @@
   web_intent_picker_controller_.reset(new WebIntentPickerController(this));
 
 #if !defined(OS_ANDROID)
   print_view_manager_.reset(new printing::PrintViewManager(this));
   sad_tab_helper_.reset(new SadTabHelper(contents));
 #endif
 
   // Create the per-tab observers.
   alternate_error_page_tab_observer_.reset(
       new AlternateErrorPageTabObserver(contents, profile()));
-  download_request_limiter_observer_.reset(
-      new DownloadRequestLimiterObserver(contents));
   webnavigation_observer_.reset(
       new extensions::WebNavigationTabObserver(contents));
   external_protocol_observer_.reset(new ExternalProtocolObserver(contents));
   pdf_tab_observer_.reset(new PDFTabObserver(this));
   plugin_observer_.reset(new PluginObserver(this));
   safe_browsing_tab_observer_.reset(
       new safe_browsing::SafeBrowsingTabObserver(this));
 
 #if !defined(OS_ANDROID)
   if (OmniboxSearchHint::IsEnabled(profile()))
@@ skipping 71 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // WebContentsObserver overrides
 
 void TabContentsWrapper::WebContentsDestroyed(WebContents* tab) {
   // Destruction of the WebContents should only be done by us from our
   // destructor. Otherwise it's very likely we (or one of the helpers we own)
   // will attempt to access the WebContents and we'll crash.
   DCHECK(in_destructor_);
 }