Add a browsertest suite for net predictor

chrome/browser/net/predictor.h

 // 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.
 
 // A Predictor object is instantiated once in the browser process, and manages
 // both preresolution of hostnames, as well as TCP/IP preconnection to expected
 // subresources.
 // Most hostname lists are provided by the renderer processes, and include URLs
 // that *might* be used in the near future by the browsing user.  One goal of
 // this class is to cause the underlying DNS structure to lookup a hostname
@@ skipping 57 matching lines @@
 typedef std::map<GURL, UrlInfo> Results;
 
 // An observer for testing.
 class PredictorObserver {
  public:
   virtual ~PredictorObserver() {}
 
   virtual void OnPreconnectUrl(const GURL& original_url,
                                const GURL& first_party_for_cookies,
                                UrlInfo::ResolutionMotivation motivation,
-                               int count) = 0;
+                               int count) {}
+  virtual void OnLearnFromNavigation(const GURL& referring_url,
+                                     const GURL& target_url) {}
 };
 
 // Predictor is constructed during Profile construction (on the UI thread),
 // but it is destroyed on the IO thread when ProfileIOData goes away. All of
 // its core state and functionality happens on the IO thread. The only UI
 // methods are initialization / shutdown related (including preconnect
 // initialization), or convenience methods that internally forward calls to
 // the IO thread.
 class Predictor {
  public:
@@ skipping 211 matching lines @@
   }
 
   bool preconnect_enabled() const {
     return preconnect_enabled_;
   }
 
   bool predictor_enabled() const {
     return predictor_enabled_;
   }
 
+  // Used only for testing.
+  void set_preconnect_enabled(bool preconnect_enabled) {

[mmenke, 2016/04/15 15:44:02]

set_preconnect_enabled_for_test

There's a clang check that _for_test / ForTest methods aren't called in
production, I believe.

[Charlie Harrison, 2016/04/20 12:36:42]

Done.

+    preconnect_enabled_ = preconnect_enabled;
+  }

[mmenke, 2016/04/15 15:44:02]

This doesn't seem threadsafe - this is accessed on both the IO and UI threads.

Unfortunately, the test fixture adds a command line switch to disable
preconnects (They break our really bad spawned test server).  I don't suppose we
can just remove that argument in SetUpCommandLine (Or whatever the test fixture
method is called)

[Charlie Harrison, 2016/04/20 12:36:42]

Hmmm. I can try that in another CL to see if anything breaks. We can always
selectively add the command line for breaking tests.

I'll leave this as is for now with the expectation that I'll find a better
solution later.

What would you think about adding another flag to override this one?

[mmenke, 2016/04/22 16:29:24]

We can't really selectively add the flag - every single test that uses the
embedded test server for a single navigation/resource will run into this.
I think adding another flag is a worse solution.

 
  private:
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, BenefitLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ShutdownWhenResolutionIsPendingTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, SingleLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ConcurrentLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, MassiveConcurrentLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueuePushPopTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueueReorderTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ReferrerSerializationTrimTest);
@@ skipping 237 matching lines @@
   // The SSLConfigService we query SNI support from (used in querying HSTS
   // redirects).
   net::SSLConfigService* ssl_config_service_;
 
   // The ProxyService, used to determine whether preresolve is useful.
   net::ProxyService* proxy_service_;
 
   // Are we currently using preconnection, rather than just DNS resolution, for
   // subresources and omni-box search URLs.
   // This is false if and only if disabled by a command line switch.
-  const bool preconnect_enabled_;
+  bool preconnect_enabled_;
 
   // Most recent suggestion from Omnibox provided via AnticipateOmniboxUrl().
   std::string last_omnibox_host_;
 
   // The time when the last preresolve was done for last_omnibox_host_.
   base::TimeTicks last_omnibox_preresolve_;
 
   // The number of consecutive requests to AnticipateOmniboxUrl() that suggested
   // preconnecting (because it was to a search service).
   int consecutive_omnibox_preconnect_count_;
@@ skipping 36 matching lines @@
 
  private:
   // These member functions return True for unittests.
   bool CanPrefetchAndPrerender() const override;
   bool CanPreresolveAndPreconnect() const override;
 };
 
 }  // namespace chrome_browser_net
 
 #endif  // CHROME_BROWSER_NET_PREDICTOR_H_