[Sync] Clean up about:sync

chrome/browser/resources/sync_internals/chrome_sync.js

 var chrome = chrome || {};
 // TODO(akalin): Add mocking code for e.g. chrome.send() so that we
 // can test this without rebuilding chrome.
 chrome.sync = chrome.sync || {};
 (function () {
 
 // This Event class is a simplified version of the one from
 // event_bindings.js.
 function Event() {
   this.listeners_ = [];
@@ skipping 22 matching lines @@
 // Returns the index of the given listener, or -1 if not found.
 Event.prototype.findListener_ = function(listener) {
   for (var i = 0; i < this.listeners_.length; i++) {
     if (this.listeners_[i] == listener) {
       return i;
     }
   }
   return -1;
 };
 
-// Fires the event.  Called by the actual event callback.
+// Fires the event.  Called by the actual event callback.  Any
+// exceptions thrown by a listener are caught and logged.
 Event.prototype.dispatch_ = function() {
   var args = Array.prototype.slice.call(arguments);
   for (var i = 0; i < this.listeners_.length; i++) {
     try {
       this.listeners_[i].apply(null, args);
     } catch (e) {
-      console.error(e);
+      if (e instanceof Error) {
+        // Non-standard, but useful.
+        console.error(e.stack);
+      } else {
+        console.error(e);
+      }
     }
   }
 };
 
 // Sync service events.
 chrome.sync.onSyncServiceStateChanged = new Event();
 
 // Notification events.
 chrome.sync.onSyncNotificationStateChange = new Event();
 chrome.sync.onSyncIncomingNotification = new Event();
@@ skipping 22 matching lines @@
 // called with the return value.
 AsyncFunction.prototype.call = function() {
   var args = Array.prototype.slice.call(arguments);
   this.callbacks_.push(args.pop());
   chrome.send(this.name_, args);
 }
 
 // Handle a reply, assuming that messages are processed in FIFO order.
 AsyncFunction.prototype.handleReply = function() {
   var args = Array.prototype.slice.call(arguments);
+  // Remove the callback before we call it since the callback may
+  // throw.
   var callback = this.callbacks_.shift();
-  try {
-    callback.apply(null, args);
-  } catch (e) {
-    console.error(e);
-  }
+  callback.apply(null, args);
 }
 
 // Sync service functions.
 chrome.sync.getAboutInfo_ = new AsyncFunction('getAboutInfo');
 chrome.sync.getAboutInfo = function(callback) {
   chrome.sync.getAboutInfo_.call(callback);
 }
 
 // Notification functions.
 chrome.sync.getNotificationState_ =
@@ skipping 97 matching lines @@
   chrome.sync.getNotificationState_.handleReply(notificationState);
 }
 
 function onGetRootNodeFinished(rootNode) {
   chrome.sync.getRootNode_.handleReply(rootNode);
 }
 
 function onGetNodeByIdFinished(node) {
   chrome.sync.getNodeById_.handleReply(node);
 }