Add flag to specify if explicitly requested download is from web.

content/public/browser/resource_dispatcher_host.h

Index: content/public/browser/resource_dispatcher_host.h
diff --git a/content/public/browser/resource_dispatcher_host.h b/content/public/browser/resource_dispatcher_host.h
index 1eb4c44593a08ef8dec55ce93bbef63d01005951..7bb8dbf73be18bc2d0d6a4e0728852eb655ec099 100644
--- a/content/public/browser/resource_dispatcher_host.h
+++ b/content/public/browser/resource_dispatcher_host.h
@@ -37,9 +37,12 @@ class CONTENT_EXPORT ResourceDispatcherHost {
   // Initiates a download by explicit request of the renderer, e.g. due to
   // alt-clicking a link.  If the download is started, |started_callback| will
   // be called on the UI thread with the DownloadId; otherwise an error code
-  // will be returned.
+  // will be returned.  |from_web| is used to indicate that the request
+  // was generated from a web page, and hence may not be as trustworthy
+  // as a browser generated request.
   virtual net::Error BeginDownload(
       scoped_ptr<net::URLRequest> request,
+      bool from_web,
       ResourceContext* context,
       int child_id,
       int route_id,