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

chrome/browser/extensions/api/dial/dial_apitest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/command_line.h"
 #include "chrome/browser/extensions/api/dial/dial_api.h"
 #include "chrome/browser/extensions/api/dial/dial_api_factory.h"
 #include "chrome/browser/extensions/api/dial/dial_registry.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/browser/extensions/extension_service.h"
@@ skipping 34 matching lines @@
   // Setup the test.
   ASSERT_TRUE(RunExtensionSubtest("dial/experimental", "device_list.html"));
 
   // Send three device list updates.
   scoped_refptr<extensions::DialAPI> api =
       extensions::DialAPIFactory::GetInstance()->GetForBrowserContext(
           profile());
   ASSERT_TRUE(api.get());
   extensions::DialRegistry::DeviceList devices;
 
-
   ResultCatcher catcher;
 
   DialDeviceData device1;
   device1.set_device_id("1");
   device1.set_label("1");
   device1.set_device_description_url(GURL("http://127.0.0.1/dd.xml"));
 
   devices.push_back(device1);
   api->SendEventOnUIThread(devices);
 
   DialDeviceData device2;
   device2.set_device_id("2");
   device2.set_label("2");
   device2.set_device_description_url(GURL("http://127.0.0.2/dd.xml"));
 
   devices.push_back(device2);
   api->SendEventOnUIThread(devices);
 
   DialDeviceData device3;
   device3.set_device_id("3");
   device3.set_label("3");
   device3.set_device_description_url(GURL("http://127.0.0.3/dd.xml"));
 
   devices.push_back(device3);
   api->SendEventOnUIThread(devices);
 
   EXPECT_TRUE(catcher.GetNextResult()) << catcher.message();
 }
 
-// Test discoverNow fails if there are no listeners. When there are no listeners
-// the DIAL API will not be active.
 IN_PROC_BROWSER_TEST_F(DialAPITest, Discovery) {
   ASSERT_TRUE(RunExtensionSubtest("dial/experimental", "discovery.html"));
 }
 
+// discoverNow does not do discovery when there are no listeners; in that case
+// the DIAL service will not be active.
+IN_PROC_BROWSER_TEST_F(DialAPITest, DiscoveryNoListeners) {
+  ASSERT_TRUE(RunExtensionSubtest("dial/experimental",
+                                  "discovery_no_listeners.html"));
+}
+
 // Make sure this API is only accessible to whitelisted extensions.
 IN_PROC_BROWSER_TEST_F(DialAPITest, NonWhitelistedExtension) {
   ResultCatcher catcher;
   catcher.RestrictToProfile(browser()->profile());
 
   ExtensionTestMessageListener listener("ready", true);
   const extensions::Extension* extension = LoadExtensionWithFlags(
       test_data_dir_.AppendASCII("dial/whitelist"),
       ExtensionBrowserTest::kFlagIgnoreManifestWarnings);
   // We should have a DIAL API not available warning.
   ASSERT_FALSE(extension->install_warnings().empty());
 
   EXPECT_TRUE(listener.WaitUntilSatisfied());
 
   listener.Reply("go");
   EXPECT_TRUE(catcher.GetNextResult()) << catcher.message();
 }
 
 IN_PROC_BROWSER_TEST_F(DialAPITest, OnError) {
   ASSERT_TRUE(RunExtensionSubtest("dial/experimental", "on_error.html"));
 }