Speculative fix for crash in DOMUIThumbnailSource.

chrome/browser/dom_ui/dom_ui_favicon_source.cc

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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/dom_ui/dom_ui_favicon_source.h"
 
 #include "app/resource_bundle.h"
 #include "base/callback.h"
+#include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/profile.h"
 #include "chrome/common/url_constants.h"
 #include "grit/app_resources.h"
 
 DOMUIFavIconSource::DOMUIFavIconSource(Profile* profile)
     : DataSource(chrome::kChromeUIFavIconHost, MessageLoop::current()),
       profile_(profile) {
 }
 
+DOMUIFavIconSource::~DOMUIFavIconSource() {
+  DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
+}
+
 void DOMUIFavIconSource::StartDataRequest(const std::string& path,
                                           bool is_off_the_record,
                                           int request_id) {
+  DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
   FaviconService* favicon_service =
       profile_->GetFaviconService(Profile::EXPLICIT_ACCESS);
   if (favicon_service) {
     FaviconService::Handle handle;
     if (path.size() > 8 && path.substr(0, 8) == "iconurl/") {
       handle = favicon_service->GetFavicon(
           GURL(path.substr(8)),
           &cancelable_consumer_,
           NewCallback(this, &DOMUIFavIconSource::OnFavIconDataAvailable));
     } else {
       handle = favicon_service->GetFaviconForURL(
           GURL(path),
           &cancelable_consumer_,
           NewCallback(this, &DOMUIFavIconSource::OnFavIconDataAvailable));
     }
     // Attach the ChromeURLDataManager request ID to the history request.
     cancelable_consumer_.SetClientData(favicon_service, handle, request_id);
   } else {
     SendResponse(request_id, NULL);
   }
 }
 
+std::string DOMUIFavIconSource::GetMimeType(const std::string&) const {
+  // We need to explicitly return a mime type, otherwise if the user tries to
+  // drag the image they get no extension.
+  return "image/png";
+}
+
 void DOMUIFavIconSource::OnFavIconDataAvailable(
     FaviconService::Handle request_handle,
     bool know_favicon,
     scoped_refptr<RefCountedMemory> data,
     bool expired,
     GURL icon_url) {
+  DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
   FaviconService* favicon_service =
       profile_->GetFaviconService(Profile::EXPLICIT_ACCESS);
   int request_id = cancelable_consumer_.GetClientData(favicon_service,
                                                       request_handle);
 
   if (know_favicon && data.get() && data->size()) {
     // Forward the data along to the networking system.
     SendResponse(request_id, data);
   } else {
     if (!default_favicon_.get()) {
       default_favicon_ =
           ResourceBundle::GetSharedInstance().LoadDataResourceBytes(
               IDR_DEFAULT_FAVICON);
     }
 
     SendResponse(request_id, default_favicon_);
   }
 }