eliminate overhead of creating two funcs/closure for each port connection

meta/crx/vapi-background.js

@@ -219,6 +219,7 @@ vAPI.messaging = {
     ports: {},
     listeners: {},
     defaultHandler: null,
+    NOOPFUNC: function(){},
     UNHANDLED: 'vAPI.messaging.notHandled'
 };
 
@@ -230,21 +231,17 @@ vAPI.messaging.listen = function(listenerName, callback) {
 
 /******************************************************************************/
 
-vAPI.messaging.onConnect = function(port) {
-    var onMessage = function(request) {
-        var callback = function(response) {
-            if ( vAPI.lastError() || response === undefined ) {
-                return;
-            }
-
-            if ( request.requestId ) {
+vAPI.messaging.onPortMessage = function(request, port) {
+    var callback = vAPI.messaging.NOOPFUNC;
+    if ( request.requestId !== undefined ) {
+        callback = function(response) {
             port.postMessage({
                 requestId: request.requestId,
                 portName: request.portName,
-                    msg: response
+                msg: response !== undefined ? response : null
             });
-            }
         };
+    }
 
     // Specific handler
     var r;
@@ -265,14 +262,19 @@ vAPI.messaging.onConnect = function(port) {
     console.error('µBlock> messaging > unknown request: %o', request);
 };
 
-    var onDisconnect = function(port) {
-        port.onDisconnect.removeListener(onDisconnect);
-        port.onMessage.removeListener(onMessage);
+/******************************************************************************/
+
+vAPI.messaging.onDisconnect = function(port) {
+    port.onDisconnect.removeListener(vAPI.messaging.onDisconnect);
+    port.onMessage.removeListener(vAPI.messaging.onPortMessage);
     delete vAPI.messaging.ports[port.name];
 };
 
-    port.onDisconnect.addListener(onDisconnect);
-    port.onMessage.addListener(onMessage);
+/******************************************************************************/
+
+vAPI.messaging.onConnect = function(port) {
+    port.onDisconnect.addListener(vAPI.messaging.onDisconnect);
+    port.onMessage.addListener(vAPI.messaging.onPortMessage);
     vAPI.messaging.ports[port.name] = port;
 };
 
@@ -286,7 +288,7 @@ vAPI.messaging.setup = function(defaultHandler) {
 
     if ( typeof defaultHandler !== 'function' ) {
         defaultHandler = function(){ return null; };
-    };
+    }
     this.defaultHandler = defaultHandler;
 
     chrome.runtime.onConnect.addListener(this.onConnect);