Change var blah_blah -> blahBlah.

chrome/browser/resources/sync_internals/traffic.js

 // 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.
 
 (function() {
   var trafficToTextButton = document.getElementById('traffic-to-text');
   var trafficDump = document.getElementById('traffic-dump');
   trafficToTextButton.addEventListener('click', function(event) {
     chrome.sync.getClientServerTraffic(printData);
 });
 
 function printData(trafficRecord) {
-  var traffic_data = '';
-  traffic_data += '===\n';
-  traffic_data += 'Client Server Traffic\n';
-  traffic_data += '===\n';
-  traffic_data += JSON.stringify(trafficRecord, null, 2);
-  traffic_data += '\n';
+  var trafficData = '';
+  trafficData += '===\n';
+  trafficData += 'Client Server Traffic\n';
+  trafficData += '===\n';
+  trafficData += JSON.stringify(trafficRecord, null, 2);
+  trafficData += '\n';
 
-  trafficDump.textContent = traffic_data;
+  trafficDump.textContent = trafficData;
 }
 })();