Allow uncaught exception messaging in Object.observe callbacks.

src/object-observe.js

Index: src/object-observe.js
diff --git a/src/object-observe.js b/src/object-observe.js
index 3af2d512075c15bb4294970ab7eadf8a92a886ab..01ce8054fdd57df55644d1aa4b366115f76dfdf2 100644
--- a/src/object-observe.js
+++ b/src/object-observe.js
@@ -567,12 +567,11 @@ function CallbackDeliverPending(callback) {
   if (!IS_NULL(pendingObservers))
     delete pendingObservers[priority];
 
+  // TODO: combine the following runtime calls for perf optimization.
   var delivered = [];
   %MoveArrayContents(callbackInfo, delivered);
+  %DeliverObservationChangeRecords(callback, delivered);
 
-  try {
-    %_CallFunction(UNDEFINED, delivered, callback);
-  } catch (ex) {}  // TODO(rossberg): perhaps log uncaught exceptions.
   return true;
 }