Fix a predictor browsertest for the PreconnectMore experiment

chrome/browser/net/predictor_browsertest.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 <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
 #include <memory>
 
@@ skipping 446 matching lines @@
     scoped_host_resolver_proc_.reset(new net::ScopedDefaultHostResolverProc(
         host_resolution_request_recorder_.get()));
     InProcessBrowserTest::SetUpInProcessBrowserTestFixture();
   }
 
   void SetUpCommandLine(base::CommandLine* command_line) override {
     command_line->AppendSwitch(
         switches::kEnableExperimentalWebPlatformFeatures);
     command_line->AppendSwitchASCII(
         switches::kEnableBlinkFeatures, kBlinkPreconnectFeature);
+    command_line->AppendSwitchASCII(switches::kEnableFeatures,
+                                    "PreconnectMore");
   }
 
   void SetUpOnMainThread() override {
     DCHECK_CURRENTLY_ON(BrowserThread::UI);
     task_runner_ = base::ThreadTaskRunnerHandle::Get();
     cross_site_test_server_->ServeFilesFromSourceDirectory("chrome/test/data/");
 
     connection_listener_.reset(new ConnectionListener());
     cross_site_connection_listener_.reset(new ConnectionListener());
     embedded_test_server()->SetConnectionListener(connection_listener_.get());
@@ skipping 110 matching lines @@
     return cross_site_test_server_.get();
   }
 
   Predictor* predictor() { return browser()->profile()->GetNetworkPredictor(); }
 
   void InstallPredictorObserver(const GURL& source_host,
                                 const GURL& cross_site_host) {
     DCHECK_CURRENTLY_ON(BrowserThread::UI);
     observer_.reset(
         new CrossSitePredictorObserver(source_host, cross_site_host));
-    BrowserThread::PostTask(
+    base::RunLoop run_loop;

[mmenke, 2016/05/16 19:10:07]

These shouldn't be needed - anything that does any network activity on the IO
thread triggered after this point will necessarily happen after this event.  The
only concern would be if we tore down the test fixture before the task runs. 
Since we always wait on some IO thread task, shouldn't be a problem there.  So
this part of the CL is fine, but I don't think it fixes anything.

[Charlie Harrison, 2016/05/16 19:13:39]

Ack. Thanks for the clarification. I'll keep it for test simplicity (readers
don't have to know that implementation detail).

+    BrowserThread::PostTaskAndReply(
         BrowserThread::IO, FROM_HERE,
         base::Bind(&PredictorBrowserTest::InstallPredictorObserverOnIOThread,
-                   base::Unretained(this), base::Unretained(predictor())));
+                   base::Unretained(this), base::Unretained(predictor())),
+        run_loop.QuitClosure());
+    run_loop.Run();
   }
 
   void InstallPredictorObserverOnIOThread(
       chrome_browser_net::Predictor* predictor) {
     DCHECK_CURRENTLY_ON(BrowserThread::IO);
     predictor->SetObserver(observer_.get());
   }
 
   // Note: For many of the tests to get to a "clean slate" mid run, they must
   // flush sockets on both the client and server.
@@ skipping 631 matching lines @@
   // Second navigation to content with an img.
   std::string img_content =
       "<img src=\"" + preconnect_url.spec() + "test.gif\">";
   NavigateToDataURLWithContent(img_content);
   connection_listener_->WaitUntilFirstConnectionRead();
   EXPECT_EQ(2u, connection_listener_->GetAcceptedSocketCount());
   EXPECT_EQ(1u, connection_listener_->GetReadSocketCount());
 }
 
 }  // namespace chrome_browser_net