Add a Cocoa version of the auto-dismissing dialog.

chrome/browser/ui/javascript_dialogs/javascript_dialog.cc

Index: chrome/browser/ui/javascript_dialogs/javascript_dialog.cc
diff --git a/cc/ipc/frame_sink_id.mojom b/chrome/browser/ui/javascript_dialogs/javascript_dialog.cc
similarity index 58%
copy from cc/ipc/frame_sink_id.mojom
copy to chrome/browser/ui/javascript_dialogs/javascript_dialog.cc
index b8fb286fe883dc8cc0782d867ed452861f85b268..add24ab5c67c8225d2e15c7120fe40c26e9ca2fa 100644
--- a/cc/ipc/frame_sink_id.mojom
+++ b/chrome/browser/ui/javascript_dialogs/javascript_dialog.cc
@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-module cc.mojom;
+#include "chrome/browser/ui/javascript_dialogs/javascript_dialog.h"
 
-struct FrameSinkId {
-  uint32 client_id;
-  uint32 sink_id;
-};
+JavaScriptDialog::~JavaScriptDialog() = default;