Revert 54771 - Enable speculative preconnection by default

Added histogram to track utilization (vs waste).

[The stability bot was reporting problems, so I'm reverting]

r=mbelshe
Review URL: http://codereview.chromium.org/3026038

TBR=jar@chromium.org
Review URL: http://codereview.chromium.org/3090011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54930 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 30 insertions, 88 deletions

diff --git a/chrome/browser/net/preconnect.cc b/chrome/browser/net/preconnect.cc
index 3872d2a..e8038ff 100644
--- a/chrome/browser/net/preconnect.cc
+++ b/chrome/browser/net/preconnect.cc
@@ -21,22 +21,18 @@ namespace chrome_browser_net {
 // static
 bool Preconnect::preconnect_despite_proxy_ = false;
 
-
-Preconnect::~Preconnect() {
-  if (!handle_.is_initialized())
-    return;
-  DCHECK(motivation_ == UrlInfo::LEARNED_REFERAL_MOTIVATED ||
-         motivation_ == UrlInfo::OMNIBOX_MOTIVATED);
-  if (motivation_ == UrlInfo::OMNIBOX_MOTIVATED)
-    handle_.socket()->SetOmniboxSpeculation();
-  else
-    handle_.socket()->SetSubresourceSpeculation();
-  handle_.Reset();
-}
+// We will deliberately leak this singular instance, which is used only for
+// callbacks.
+// static
+Preconnect* Preconnect::callback_instance_;
 
 // static
 void Preconnect::PreconnectOnUIThread(const GURL& url,
     UrlInfo::ResolutionMotivation motivation) {
+  // Try to do connection warming for this search provider.
+  URLRequestContextGetter* getter = Profile::GetDefaultRequestContext();
+  if (!getter)
+    return;
   // Prewarm connection to Search URL.
   ChromeThread::PostTask(
       ChromeThread::IO,
@@ -61,13 +57,6 @@ static void HistogramPreconnectStatus(ProxyStatus status) {
 // static
 void Preconnect::PreconnectOnIOThread(const GURL& url,
     UrlInfo::ResolutionMotivation motivation) {
-  scoped_refptr<Preconnect> preconnect = new Preconnect(motivation);
-  // TODO(jar): Should I use PostTask for LearnedSubresources to delay the
-  // preconnection a tad?
-  preconnect->Connect(url);
-}
-
-void Preconnect::Connect(const GURL& url) {
   URLRequestContextGetter* getter = Profile::GetDefaultRequestContext();
   if (!getter)
     return;
@@ -75,9 +64,6 @@ void Preconnect::Connect(const GURL& url) {
     LOG(DFATAL) << "This must be run only on the IO thread.";
     return;
   }
-
-  AddRef();  // Stay alive until socket is available.
-
   URLRequestContext* context = getter->GetURLRequestContext();
 
   if (preconnect_despite_proxy_) {
@@ -100,12 +86,16 @@ void Preconnect::Connect(const GURL& url) {
     }
   }
 
-  UMA_HISTOGRAM_ENUMERATION("Net.PreconnectMotivation", motivation_,
+  UMA_HISTOGRAM_ENUMERATION("Net.PreconnectMotivation", motivation,
                             UrlInfo::MAX_MOTIVATED);
 
   net::HttpTransactionFactory* factory = context->http_transaction_factory();
   net::HttpNetworkSession* session = factory->GetSession();
 
+  net::ClientSocketHandle handle;
+  if (!callback_instance_)
+    callback_instance_ = new Preconnect;
+
   scoped_refptr<net::TCPSocketParams> tcp_params =
       new net::TCPSocketParams(url.host(), url.EffectiveIntPort(), net::LOW,
                                GURL(), false);
@@ -113,19 +103,6 @@ void Preconnect::Connect(const GURL& url) {
   net::HostPortPair endpoint(url.host(), url.EffectiveIntPort());
   std::string group_name = endpoint.ToString();
 
-  // It almost doesn't matter whether we use net::LOWEST or net::HIGHEST
-  // priority here, as we won't make a request, and will surrender the created
-  // socket to the pool as soon as we can.  However, we would like to mark the
-  // speculative socket as such, and IF we use a net::LOWEST priority, and if
-  // a navigation asked for a socket (after us) then it would get our socket,
-  // and we'd get its later-arriving socket, which might make us record that
-  // the speculation didn't help :-/.  By using net::HIGHEST, we ensure that
-  // a socket is given to us if "we asked first" and this allows us to mark it
-  // as speculative, and better detect stats (if it gets used).
-  // TODO(jar): histogram to see how often we accidentally use a previously-
-  // unused socket, when a previously used socket was available.
-  net::RequestPriority priority = net::HIGHEST;
-
   if (url.SchemeIs("https")) {
     group_name = StringPrintf("ssl/%s", group_name.c_str());
 
@@ -143,20 +120,21 @@ void Preconnect::Connect(const GURL& url) {
     const scoped_refptr<net::SSLClientSocketPool>& pool =
         session->ssl_socket_pool();
 
-    handle_.Init(group_name, ssl_params, priority, this, pool,
-                 net::BoundNetLog());
+    handle.Init(group_name, ssl_params, net::LOWEST, callback_instance_, pool,
+                net::BoundNetLog());
+    handle.Reset();
     return;
   }
 
   const scoped_refptr<net::TCPClientSocketPool>& pool =
       session->tcp_socket_pool();
-  handle_.Init(group_name, tcp_params, priority, this, pool,
-               net::BoundNetLog());
+  handle.Init(group_name, tcp_params, net::LOWEST, callback_instance_, pool,
+              net::BoundNetLog());
+  handle.Reset();
 }
 
 void Preconnect::RunWithParams(const Tuple1<int>& params) {
-  if (params.a < 0 && handle_.socket())
-    handle_.socket()->Disconnect();
-  Release();
+  // This will rarely be called, as we reset the connection just after creating.
+  NOTREACHED();
 }
 }  // chrome_browser_net
diff --git a/chrome/browser/net/preconnect.h b/chrome/browser/net/preconnect.h
index f7d574d..d773636 100644
--- a/chrome/browser/net/preconnect.h
+++ b/chrome/browser/net/preconnect.h
@@ -19,8 +19,7 @@
 
 namespace chrome_browser_net {
 
-class Preconnect : public net::CompletionCallback,
-                   public base::RefCountedThreadSafe<Preconnect> {
+class Preconnect : public net::CompletionCallback {
  public:
   // Try to preconnect.  Typically motivated by OMNIBOX to reach search service.
   static void PreconnectOnUIThread(const GURL& url,
@@ -36,15 +35,11 @@ class Preconnect : public net::CompletionCallback,
   }
 
  private:
-  friend class base::RefCountedThreadSafe<Preconnect>;
+  Preconnect() {}
 
-  explicit Preconnect(UrlInfo::ResolutionMotivation motivation)
-      : motivation_(motivation) {
-  }
-  ~Preconnect();
-
-  // Request actual connection.
-  void Connect(const GURL& url);
+  // Supply an instance that could have been used in an IO callback, but will
+  // never actually be used (because we reset the connection so quickly).
+  static Preconnect* callback_instance_;
 
   // IO Callback which whould be performed when the connection is established.
   virtual void RunWithParams(const Tuple1<int>& params);
@@ -55,15 +50,6 @@ class Preconnect : public net::CompletionCallback,
   // much work anway).
   static bool preconnect_despite_proxy_;
 
-  // The handle holding the request. We need this so that we can mark the
-  // request as speculative when an actual socket is bound to it.
-  net::ClientSocketHandle handle_;
-
-  // Generally either LEARNED_REFERAL_MOTIVATED or OMNIBOX_MOTIVATED to indicate
-  // why we were trying to do a preconnection.
-  const UrlInfo::ResolutionMotivation motivation_;
-
-
   DISALLOW_COPY_AND_ASSIGN(Preconnect);
 };
 }  // chrome_browser_net
diff --git a/chrome/browser/net/predictor.cc b/chrome/browser/net/predictor.cc
index 5c1b518..eb4992c 100644
--- a/chrome/browser/net/predictor.cc
+++ b/chrome/browser/net/predictor.cc
@@ -149,20 +149,6 @@ void Predictor::PredictFrameSubresources(const GURL& url) {
   Referrers::iterator it = referrers_.find(url);
   if (referrers_.end() == it)
     return;
-  ChromeThread::PostTask(
-      ChromeThread::IO,
-      FROM_HERE,
-      NewRunnableMethod(this,
-                        &Predictor::PrepareFrameSubresources, url));
-}
-
-void Predictor::PrepareFrameSubresources(const GURL& url) {
-  DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO));
-  DCHECK(url.GetWithEmptyPath() == url);
-  Referrers::iterator it = referrers_.find(url);
-  if (referrers_.end() == it)
-    return;
-
   Referrer* referrer = &(it->second);
   referrer->IncrementUseCount();
   const UrlInfo::ResolutionMotivation motivation =
diff --git a/chrome/browser/net/predictor.h b/chrome/browser/net/predictor.h
index c613093..a5b71e7 100644
--- a/chrome/browser/net/predictor.h
+++ b/chrome/browser/net/predictor.h
@@ -83,11 +83,8 @@ class Predictor : public base::RefCountedThreadSafe<Predictor> {
   void Resolve(const GURL& url,
                UrlInfo::ResolutionMotivation motivation);
 
-  // Instigate pre-connection to any URLs, or pre-resolution of related host,
-  // that we predict will be needed after this navigation (typically
-  // more-embedded resources on a page).  This method will actually post a task
-  // to do the actual work, so as not to jump ahead of the frame navigation that
-  // instigated this activity.
+  // Instigate pre-connection to any URLs we predict will be needed after this
+  // navigation (typically more-embedded resources on a page).
   void PredictFrameSubresources(const GURL& url);
 
   // Record details of a navigation so that we can preresolve the host name
@@ -141,6 +138,8 @@ class Predictor : public base::RefCountedThreadSafe<Predictor> {
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueueReorderTest);
   friend class WaitForResolutionHelper;  // For testing.
 
+  ~Predictor();
+
   class LookupRequest;
 
   // A simple priority queue for handling host names.
@@ -175,13 +174,6 @@ class Predictor : public base::RefCountedThreadSafe<Predictor> {
   // in a Referrer instance, which is a value in this map.
   typedef std::map<GURL, Referrer> Referrers;
 
-  ~Predictor();
-
-  // Perform actual resolution or preconnection to subresources now.  This is
-  // an internal worker method that is reached via a post task from
-  // PredictFrameSubresources().
-  void PrepareFrameSubresources(const GURL& url);
-
   // Only for testing. Returns true if hostname has been successfully resolved
   // (name found).
   bool WasFound(const GURL& url) const {