Update references to the extension messaging APIs to point to the "runtime"

tools/page_cycler/webpagereplay/extension/background.js

Index: tools/page_cycler/webpagereplay/extension/background.js
diff --git a/tools/page_cycler/webpagereplay/extension/background.js b/tools/page_cycler/webpagereplay/extension/background.js
index 207979e88605cfd3238f85721bf7e6794b8c0dd6..e03c230b86e3229ec2218456bc358109d8fb49a6 100644
--- a/tools/page_cycler/webpagereplay/extension/background.js
+++ b/tools/page_cycler/webpagereplay/extension/background.js
@@ -318,11 +318,11 @@ function Run() {
   sessionLoader.run();
 }
 
-chrome.extension.onConnect.addListener(function(port) {
+chrome.runtime.onConnect.addListener(function(port) {
   port.onMessage.addListener(function(data) {
     if (data.message == "start") {
       window.benchmarkConfiguration = data.benchmark;
       Run()
     }
   });
-});
+});