Rewrite DownloadsApiTest in C++.

chrome/browser/download/chrome_download_manager_delegate.cc

Index: chrome/browser/download/chrome_download_manager_delegate.cc
diff --git a/chrome/browser/download/chrome_download_manager_delegate.cc b/chrome/browser/download/chrome_download_manager_delegate.cc
index 9fb173e4b8a5909399d2666113efb13d70aec3bf..b61955191919f7e675dd4591f32d41214051ae44 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -118,7 +118,8 @@ void ChromeDownloadManagerDelegate::SetDownloadManager(DownloadManager* dm) {
   download_history_->Load(
       base::Bind(&DownloadManager::OnPersistentStoreQueryComplete,
                  base::Unretained(dm)));
-  extension_event_router_.reset(new ExtensionDownloadsEventRouter(profile_));
+  extension_event_router_.reset(new ExtensionDownloadsEventRouter(
+      profile_, download_manager_));
 }
 
 void ChromeDownloadManagerDelegate::Shutdown() {