Adding a DownloadRestrictions group policy.

content/public/test/fake_download_item.cc

Index: content/public/test/fake_download_item.cc
diff --git a/content/public/test/fake_download_item.cc b/content/public/test/fake_download_item.cc
index 4ae0a1b50527a4f3b4f87412a535c4dfd3207a28..49f7bc00a1cb8f05b081bf39f828b0321a64beb8 100644
--- a/content/public/test/fake_download_item.cc
+++ b/content/public/test/fake_download_item.cc
@@ -409,7 +409,8 @@ WebContents* FakeDownloadItem::GetWebContents() const {
   return nullptr;
 }
 
-void FakeDownloadItem::OnContentCheckCompleted(DownloadDangerType danger_type) {
+void FakeDownloadItem::OnContentCheckCompleted(DownloadDangerType danger_type,
+                                               DownloadInterruptReason reason) {
   NOTREACHED();
 }