Fix instrument()

Author: eriwen

spec/stacktrace-spec.js

@@ -109,7 +109,7 @@ describe('StackTrace', function () {
         it('wraps given function and calls given callback when called', function(done) {
             function interestingFn() { return 'something'; }
             var wrapped = StackTrace.instrument(interestingFn, callback, done.fail);
-            wrapped();
+            expect(wrapped()).toBe('something');
 
             function callback(stackFrames) {
                 if (stackFrames[0].fileName) { // Work around IE9-

stacktrace.js

@@ -127,7 +127,7 @@
             var instrumented = function StackTrace$$instrumented() {
                 try {
                     this.get().then(callback, errback)['catch'](errback);
-                    fn.apply(thisArg || this, arguments);
+                    return fn.apply(thisArg || this, arguments);
                 } catch (e) {
                     if (_isShapedLikeParsableError(e)) {
                         this.fromError(e).then(callback, errback)['catch'](errback);