Adding a DownloadRestrictions group policy.

content/public/test/fake_download_item.h

Index: content/public/test/fake_download_item.h
diff --git a/content/public/test/fake_download_item.h b/content/public/test/fake_download_item.h
index 504477ccb6f24d55934f1011706e966b74ca9bf3..b0b44f978f6309a89e893e4a02880a4de8d47768 100644
--- a/content/public/test/fake_download_item.h
+++ b/content/public/test/fake_download_item.h
@@ -136,7 +136,8 @@ class FakeDownloadItem : public DownloadItem {
   bool IsTransient() const override;
   BrowserContext* GetBrowserContext() const override;
   WebContents* GetWebContents() const override;
-  void OnContentCheckCompleted(DownloadDangerType danger_type) override;
+  void OnContentCheckCompleted(DownloadDangerType danger_type,
+                               DownloadInterruptReason reason) override;
   void SetOpenWhenComplete(bool open) override;
   void SetOpened(bool opened) override;
   void SetDisplayName(const base::FilePath& name) override;