[Extensions] Make Event::restrict_to_browser_context const.

chrome/browser/extensions/api/downloads/downloads_api.cc

Index: chrome/browser/extensions/api/downloads/downloads_api.cc
diff --git a/chrome/browser/extensions/api/downloads/downloads_api.cc b/chrome/browser/extensions/api/downloads/downloads_api.cc
index 725dc57dc3d118b302462ebf9801662bf9063e48..dab655002bfd6d921758811eed2c422735792641 100644
--- a/chrome/browser/extensions/api/downloads/downloads_api.cc
+++ b/chrome/browser/extensions/api/downloads/downloads_api.cc
@@ -1886,15 +1886,16 @@ void ExtensionDownloadsEventRouter::DispatchEvent(
   args->Append(std::move(arg));
   std::string json_args;
   base::JSONWriter::Write(*args, &json_args);
-  std::unique_ptr<Event> event(
-      new Event(histogram_value, event_name, std::move(args)));
   // The downloads system wants to share on-record events with off-record
   // extension renderers even in incognito_split_mode because that's how
   // chrome://downloads works. The "restrict_to_profile" mechanism does not
   // anticipate this, so it does not automatically prevent sharing off-record
   // events with on-record extension renderers.

[Devlin, 2017/05/24 16:08:18]

This makes sense (at least, somewhat), but it's still the wrong granularity. 
Instead, we should introduce something like "include incognito" in the event
structure to handle this case, because otherwise this will broadcast to
unrelated profiles.  Can we add a TODO?

[lazyboy, 2017/05/24 19:19:32]

Added a crbug. Added TODO here and in Event constructor.

-  event->restrict_to_browser_context =
+  Profile* restrict_to_browser_context =
       (include_incognito && !profile_->IsOffTheRecord()) ? NULL : profile_;
+  auto event =
+      base::MakeUnique<Event>(histogram_value, event_name, std::move(args),
+                              restrict_to_browser_context);
   event->will_dispatch_callback = will_dispatch_callback;
   EventRouter::Get(profile_)->BroadcastEvent(std::move(event));
   DownloadsNotificationSource notification_source;