Reject connection attempts without prompt if target app doesn't handle the event anyway.

chrome/browser/extensions/api/messaging/message_service.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/messaging/message_service.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/json/json_writer.h"
@@ skipping 12 matching lines @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/tab_contents/tab_util.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
+#include "extensions/browser/event_router.h"
 #include "extensions/browser/extension_host.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/extensions_browser_client.h"
 #include "extensions/browser/lazy_background_task_queue.h"
 #include "extensions/browser/pref_names.h"
 #include "extensions/browser/process_manager.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_constants.h"
 #include "extensions/common/manifest_handlers/background_info.h"
@@ skipping 293 matching lines @@
     // Give the user a chance to accept an incognito connection from the web if
     // they haven't already, with the conditions:
     // - Only for spanning-mode incognito. We don't want the complication of
     //   spinning up an additional process here which might need to do some
     //   setup that we're not expecting.
     // - Only for extensions that can't normally be enabled in incognito, since
     //   that surface (e.g. chrome://extensions) should be the only one for
     //   enabling in incognito. In practice this means platform apps only.
     if (!is_web_connection || IncognitoInfo::IsSplitMode(target_extension) ||
         target_extension->can_be_incognito_enabled()) {
-      DispatchOnDisconnect(source, receiver_port_id,
-                           kReceivingEndDoesntExistError);
+      OnOpenChannelAllowed(params.Pass(), false);
       return;
     }
 
+    // If the target extension isn't even listening for connect/message events,
+    // there is no need to go any further and the connection should be
+    // rejected without showing a prompt. See http://crbug.com/442497
+    EventRouter* event_router = EventRouter::Get(context);
+    const char* const events[] = {"runtime.onConnectExternal",
+                                  "runtime.onMessageExternal",
+                                  "extension.onRequestExternal",
+                                  nullptr};
+    bool has_event_listener = false;
+    for (const char* const* event = events; *event; event++) {
+      has_event_listener |=
+          event_router->ExtensionHasEventListener(target_extension_id, *event);
+    }
+    if (!has_event_listener) {
+      OnOpenChannelAllowed(params.Pass(), false);
+      return;
+    }
+
     // This check may show a dialog.
     IncognitoConnectability::Get(context)
         ->Query(target_extension, source_contents, source_url,
                 base::Bind(&MessageService::OnOpenChannelAllowed,
                            weak_factory_.GetWeakPtr(), base::Passed(&params)));
     return;
   }
 
   OnOpenChannelAllowed(params.Pass(), true);
 }
@@ skipping 506 matching lines @@
                                              int channel_id) {
   MessageChannelMap::iterator channel_iter = channels_.find(channel_id);
   if (channel_iter != channels_.end()) {
     for (const PendingMessage& message : queue) {
       DispatchMessage(message.first, channel_iter->second, message.second);
     }
   }
 }
 
 }  // namespace extensions