Make sure ports are closed when they're no longer used.

chrome/common/extensions/docs/messaging.html

Index: chrome/common/extensions/docs/messaging.html
diff --git a/chrome/common/extensions/docs/messaging.html b/chrome/common/extensions/docs/messaging.html
index 951f969b6c337bb5d15c7044e71eeb317dcb89b8..0123757a100cfd3adedd57f09e25d6bc988a596c 100644
--- a/chrome/common/extensions/docs/messaging.html
+++ b/chrome/common/extensions/docs/messaging.html
@@ -273,9 +273,7 @@ chrome.tabs.getSelected(null, function(tab) {
 On the receiving end, you need to set up an
 <a href="extension.html#event-onRequest">chrome.extension.onRequest</a>
 event listener to handle the message. This looks the same from a content
-script or extension page. The request will remain open until you call
-sendResponse, so it is good practice to call sendResponse with an empty
-object to allow the request to be cleaned up.
+script or extension page.
 </p><pre>chrome.extension.onRequest.addListener(
   function(request, sender, sendResponse) {
     console.log(sender.tab ?
@@ -283,8 +281,6 @@ object to allow the request to be cleaned up.
                 "from the extension");
     if (request.greeting == "hello")
       sendResponse({farewell: "goodbye"});
-    else
-      sendResponse({}); // snub them.
   });
 </pre>
 <p class="note">
@@ -379,7 +375,7 @@ methods. Here's an example of each:
 chrome.extension.onRequestExternal.addListener(
   function(request, sender, sendResponse) {
     if (sender.id == blacklistedExtension)
-      sendResponse({});  // don't allow this extension access
+      return;  // don't allow this extension access
     else if (request.getTargetData)
       sendResponse({targetData: targetData});
     else if (request.activateLasers) {