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

chrome/browser/ui/tab_contents/tab_contents_wrapper.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_TAB_CONTENTS_TAB_CONTENTS_WRAPPER_H_
 #define CHROME_BROWSER_UI_TAB_CONTENTS_TAB_CONTENTS_WRAPPER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/property_bag.h"
 #include "content/public/browser/web_contents_observer.h"
 
 class AlternateErrorPageTabObserver;
 class AutocompleteHistoryManager;
 class AutofillManager;
 class AutofillExternalDelegate;
 class AutomationTabHelper;
 class BlockedContentTabHelper;
 class BookmarkTabHelper;
 class ConstrainedWindowTabHelper;
 class CoreTabHelper;
-class DownloadRequestLimiterObserver;
 class ExtensionTabHelper;
 class ExternalProtocolObserver;
 class FaviconTabHelper;
 class FindTabHelper;
 class HistoryTabHelper;
 class HungPluginTabHelper;
 class InfoBarTabHelper;
 class OmniboxSearchHint;
 class PasswordManager;
 class PasswordManagerDelegate;
@@ skipping 32 matching lines @@
 class PrintPreviewMessageHandler;
 }
 
 namespace safe_browsing {
 class SafeBrowsingTabObserver;
 }
 
 // Wraps WebContents and all of its supporting objects in order to control
 // their ownership and lifetime.
 //
+// WARNING: Not every place where HTML can run has a TabContentsWrapper. This
+// class is *only* used in a visible, actual, tab inside a browser. Examples of
+// things that do not have tab wrappers include:
+// - Extension background pages and popup bubbles
+// - HTML notification bubbles
+// - Screensavers on Chrome OS
+// - Other random places we decide to display HTML over time
+//
+// Consider carefully whether your feature is something that makes sense only
+// when a tab is displayed, or could make sense in other cases we use HTML. It
+// may makes sense to push down into WebContents and make configurable, or at
+// least to make easy for other WebContents hosts to include and support.
+//
 // TODO(avi): Eventually, this class will become TabContents as far as
 // the browser front-end is concerned.
 class TabContentsWrapper : public content::WebContentsObserver {
  public:
   // Takes ownership of |contents|, which must be heap-allocated (as it lives
   // in a scoped_ptr) and can not be NULL.
   explicit TabContentsWrapper(content::WebContents* contents);
   virtual ~TabContentsWrapper();
 
   // Create a TabContentsWrapper with the same state as this one. The returned
@@ skipping 176 matching lines @@
   scoped_ptr<TranslateTabHelper> translate_tab_helper_;
 
   // Handles displaying a web intents picker to the user.
   scoped_ptr<WebIntentPickerController> web_intent_picker_controller_;
 
   // Per-tab observers ---------------------------------------------------------
   // (These provide no API for callers; objects that need to exist 1:1 with tabs
   // and silently do their thing live here.)
 
   scoped_ptr<AlternateErrorPageTabObserver> alternate_error_page_tab_observer_;
-  scoped_ptr<DownloadRequestLimiterObserver> download_request_limiter_observer_;
   scoped_ptr<extensions::WebNavigationTabObserver> webnavigation_observer_;
   scoped_ptr<ExternalProtocolObserver> external_protocol_observer_;
   scoped_ptr<OmniboxSearchHint> omnibox_search_hint_;
 #if defined(ENABLE_ONE_CLICK_SIGNIN)
   scoped_ptr<OneClickSigninHelper> one_click_signin_helper_;
 #endif
   scoped_ptr<PDFTabObserver> pdf_tab_observer_;
   scoped_ptr<PluginObserver> plugin_observer_;
   scoped_ptr<printing::PrintPreviewMessageHandler> print_preview_;
   scoped_ptr<safe_browsing::SafeBrowsingTabObserver>
       safe_browsing_tab_observer_;
 
   // WebContents (MUST BE LAST) ------------------------------------------------
 
   // If true, we're running the destructor.
   bool in_destructor_;
 
   // The supporting objects need to outlive the WebContents dtor (as they may
   // be called upon during its execution). As a result, this must come last
   // in the list.
   scoped_ptr<content::WebContents> web_contents_;
 
   DISALLOW_COPY_AND_ASSIGN(TabContentsWrapper);
 };
 
 #endif  // CHROME_BROWSER_UI_TAB_CONTENTS_TAB_CONTENTS_WRAPPER_H_