Created a DownloadManager interface, for use in unit tests..

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 690ae50e3d3b86474bc4b5da7a02d1ce4a7087f1..57bbb65b6d2480cc66bc786c5a8318373b48fb3c 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -57,11 +57,12 @@ bool ChromeDownloadManagerDelegate::IsExtensionDownload(
       UserScript::IsURLUserScript(item->GetURL(), item->mime_type());
 }
 
-void ChromeDownloadManagerDelegate::SetDownloadManager(DownloadManager* dm) {
+void ChromeDownloadManagerDelegate::SetDownloadManager(
+    DownloadManagerInterface* dm) {
   download_manager_ = dm;
   download_history_.reset(new DownloadHistory(profile_));
   download_history_->Load(
-      base::Bind(&DownloadManager::OnPersistentStoreQueryComplete,
+      base::Bind(&DownloadManagerInterface::OnPersistentStoreQueryComplete,
                  base::Unretained(dm)));
 }
 
@@ -388,8 +389,8 @@ void ChromeDownloadManagerDelegate::CheckVisitedReferrerBeforeDone(
     // 1) using the default download directory.
     // 2) prompting the user.
     if (state.prompt_user_for_save_location &&
-        !download_manager_->last_download_path().empty()) {
-      state.suggested_path = download_manager_->last_download_path();
+        !download_manager_->LastDownloadPath().empty()) {
+      state.suggested_path = download_manager_->LastDownloadPath();
     } else {
       state.suggested_path = download_prefs_->download_path();
     }