Don't set lastError if chrome.dial.discoverNow() can't start.

chrome/test/data/extensions/api_test/dial/experimental/discovery_no_listeners.js

Index: chrome/test/data/extensions/api_test/dial/experimental/discovery_no_listeners.js
diff --git a/chrome/test/data/extensions/api_test/dial/experimental/discovery.js b/chrome/test/data/extensions/api_test/dial/experimental/discovery_no_listeners.js
similarity index 64%
copy from chrome/test/data/extensions/api_test/dial/experimental/discovery.js
copy to chrome/test/data/extensions/api_test/dial/experimental/discovery_no_listeners.js
index 917462c41ce488ca7ee30b460dc56aa49047dba2..f45c5d30c8ae6aa66420908cde1bf420a2a6723f 100644
--- a/chrome/test/data/extensions/api_test/dial/experimental/discovery.js
+++ b/chrome/test/data/extensions/api_test/dial/experimental/discovery_no_listeners.js
@@ -4,15 +4,16 @@
 
 onload = function() {
   chrome.test.runTests([
-    function discovery() {
-      var discoverNowShouldFail = function(result) {
+    function discoverNowWithoutListeners() {
+      var discoverNowCallback = function(result) {
+        chrome.test.assertNoLastError();
         if (!result) {

[Wez, 2014/08/28 19:59:52]

nit: Should we still be asserting that typeof(result) == "boolean" before
testing that it equates to false?

[mark a. foltz, 2014/08/28 20:14:50]

Done.

           chrome.test.succeed();
         } else {
           chrome.test.fail();
         }
       };
-      chrome.dial.discoverNow(discoverNowShouldFail);
+      chrome.dial.discoverNow(discoverNowCallback);
     }
   ]);
 };