Chrome extension: Debugger API does not fire event -

i want listen timeline events happened in tab, create extension

chrome.browseraction.onclicked.addlistener(function(tab) {     var tabid = tab.id;      console.log("tabid = ", tabid);      if (running === false) {         checkavailable();          chrome.debugger.attach({             tabid: tabid         }, protocolversion, function() {             running = true;              if (chrome.runtime.lasterror) {                 console.log(chrome.runtime.lasterror.message);                 return;             }              chrome.debugger.sendcommand({                 tabid: tabid             }, "tracing.start", { "maxcallstackdepth" : 5 }, function(response) {                  console.log(response);                               // listening responses timeline                 chrome.debugger.onevent.addlistener(function(tabid, method, params) {                     console.log("params = ", params);                 });             });                chrome.debugger.ondetach.addlistener(function (source, reason) {                 running = false;             });         });             } else {         chrome.debugger.detach({             tabid: tabid         }, null);         running = false;     } });  

after clicking icon see yellow bar @ top of page , message "extension debugging page".

however, after f5 not see extension listen timeline events.

it looks event has not been assigned.

chrome.debugger.onevent.addlistener(function(tabid, method, params) {     console.log("params = ", params); }); 

any ideas?