[Downloads] Ask DownloadHistory if a download was from history.

chrome/browser/download/download_service.h

Index: chrome/browser/download/download_service.h
diff --git a/chrome/browser/download/download_service.h b/chrome/browser/download/download_service.h
index 1e0ad634b1105b115522e155717c9b5e4acfae61..2cb9df8fc2d1be534e4a85713859e8aec3423af3 100644
--- a/chrome/browser/download/download_service.h
+++ b/chrome/browser/download/download_service.h
@@ -31,8 +31,8 @@ class DownloadService : public KeyedService {
 
   // Get the interface to the history system. Returns NULL if profile is
   // incognito or if the DownloadManager hasn't been created yet or if there is
-  // no HistoryService for profile.
-  DownloadHistory* GetDownloadHistory();
+  // no HistoryService for profile. Virtual for testing.
+  virtual DownloadHistory* GetDownloadHistory();
 
 #if !defined(OS_ANDROID)
   ExtensionDownloadsEventRouter* GetExtensionEventRouter() {
@@ -84,6 +84,8 @@ class DownloadService : public KeyedService {
   // The UI controller is responsible for observing the download manager and
   // notifying the UI of any new downloads. Its lifetime matches that of the
   // associated download manager.
+  // Note on destruction order: download_ui_ depends on download_history_ and
+  // should be destroyed before the latter.
   scoped_ptr<DownloadUIController> download_ui_;
 
   // On Android, GET downloads are not handled by the DownloadManager.