Delay DownloadManager creation by adding a callback queue to DownloadService

chrome/browser/download/download_extension_api.cc

 // Copyright (c) 2011 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/download/download_extension_api.h"
 
 #include <algorithm>
 #include <cctype>
 #include <iterator>
 #include <set>
 #include <string>
 
 #include "base/bind.h"
+#include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "base/string16.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 443 matching lines @@
   json->SetInteger(kTotalBytesKey, item->GetTotalBytes());
   if (item->GetState() == DownloadItem::INTERRUPTED)
     json->SetInteger(kErrorKey, static_cast<int>(item->GetLastReason()));
   // TODO(benjhayden): Implement endTime and fileSize.
   // json->SetInteger(kEndTimeKey, -1);
   json->SetInteger(kFileSizeKey, item->GetTotalBytes());
   return json;
 }
 }  // anonymous namespace
 
-ExtensionDownloadsEventRouter::ExtensionDownloadsEventRouter(
-    Profile* profile)
+ExtensionDownloadsEventRouter::ExtensionDownloadsEventRouter(Profile* profile)
   : profile_(profile),
-    manager_(
-        profile ?
-        DownloadServiceFactory::GetForProfile(profile)->GetDownloadManager() :
-        NULL) {
+    manager_(NULL) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(profile_);
-  DCHECK(manager_);
+  // Register a callback with the DownloadService for this profile to be called
+  // when it creates the DownloadManager, or now if the manager already exists.
+  DownloadServiceFactory::GetForProfile(profile)->OnManagerCreated(base::Bind(
+      &ExtensionDownloadsEventRouter::Init, base::Unretained(this)));
+}
+
+// The only public methods on this class are ModelChanged() and
+// ManagerGoingDown(), and they are only called by DownloadManager, so
+// there's no way for any methods on this class to be called before
+// DownloadService calls Init() via the OnManagerCreated Callback above.
+void ExtensionDownloadsEventRouter::Init(DownloadManager* manager) {
+  DCHECK(manager_ == NULL);
+  manager_ = manager;
   manager_->AddObserver(this);
 }
 
 ExtensionDownloadsEventRouter::~ExtensionDownloadsEventRouter() {
   if (manager_ != NULL)
     manager_->RemoveObserver(this);
 }
 
 void ExtensionDownloadsEventRouter::ModelChanged() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ skipping 49 matching lines @@
   ListValue args;
   args.Append(arg);
   std::string json_args;
   base::JSONWriter::Write(&args, false, &json_args);
   profile_->GetExtensionEventRouter()->DispatchEventToRenderers(
       event_name,
       json_args,
       profile_,
       GURL());
 }