permissionrequest API for guest Download.

content/public/browser/web_contents_delegate.h

Index: content/public/browser/web_contents_delegate.h
diff --git a/content/public/browser/web_contents_delegate.h b/content/public/browser/web_contents_delegate.h
index 6705514a7bc03dd437982049294404eedc0e92ab..7371bda8077e25e20e74a7d286b4ae41380148e0 100644
--- a/content/public/browser/web_contents_delegate.h
+++ b/content/public/browser/web_contents_delegate.h
@@ -220,9 +220,11 @@ class CONTENT_EXPORT WebContentsDelegate {
   virtual void WebContentsFocused(WebContents* contents) {}
 
   // Asks the delegate if the given tab can download.
-  virtual bool CanDownload(RenderViewHost* render_view_host,
+  // Invoking the |callback| synchronously is OK.
+  virtual void CanDownload(RenderViewHost* render_view_host,
                            int request_id,
-                           const std::string& request_method);
+                           const std::string& request_method,
+                           const base::Callback<void(bool)>& callback);
 
   // Return much extra vertical space should be allotted to the
   // render view widget during various animations (e.g. infobar closing).