Reland 54771 (and 54795) To enable TCP Preconnection by default

I pulled out the code to update the socket connectivity stats.

I added defensive code which should preclude the crash that 
was reported on the stability bot.

I added a second call to update the stats from
~ClientSocketHandle to ensure that we updated the
related ClientSocket when we are torn down.

As noted in the original checkin:

Enable speculative preconnection by default

Added histogram to track preconnection utilization (vs waste).

BUG=42694
r=mbelshe
Review URL: http://codereview.chromium.org/3050040

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55197 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 69 insertions, 0 deletions

diff --git a/net/socket/client_socket.cc b/net/socket/client_socket.cc
new file mode 100644
index 0000000..c0c62cd
--- /dev/null
+++ b/net/socket/client_socket.cc
@@ -0,0 +1,69 @@
+// Copyright (c) 2010 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 "net/socket/client_socket.h"
+
+#include "base/histogram.h"
+
+namespace net {
+
+ClientSocket::ClientSocket()
+    : was_ever_connected_(false),
+      omnibox_speculation_(false),
+      subresource_speculation_(false),
+      was_used_to_transmit_data_(false) {}
+
+ClientSocket::~ClientSocket() {
+  EmitPreconnectionHistograms();
+}
+
+void ClientSocket::EmitPreconnectionHistograms() const {
+  DCHECK(!subresource_speculation_ || !omnibox_speculation_);
+  // 0 ==> non-speculative, never connected.
+  // 1 ==> non-speculative never used (but connected).
+  // 2 ==> non-speculative and used.
+  // 3 ==> omnibox_speculative never connected.
+  // 4 ==> omnibox_speculative never used (but connected).
+  // 5 ==> omnibox_speculative and used.
+  // 6 ==> subresource_speculative never connected.
+  // 7 ==> subresource_speculative never used (but connected).
+  // 8 ==> subresource_speculative and used.
+  int result;
+  if (was_used_to_transmit_data_)
+    result = 2;
+  else if (was_ever_connected_)
+    result = 1;
+  else
+    result = 0;  // Never used, and not really connected.
+
+  if (omnibox_speculation_)
+    result += 3;
+  else if (subresource_speculation_)
+    result += 6;
+  UMA_HISTOGRAM_ENUMERATION("Net.PreconnectUtilization", result, 9);
+}
+
+void ClientSocket::SetSubresourceSpeculation() {
+  if (was_used_to_transmit_data_)
+    return;
+  subresource_speculation_ = true;
+}
+
+void ClientSocket::SetOmniboxSpeculation() {
+  if (was_used_to_transmit_data_)
+    return;
+  omnibox_speculation_ = true;
+}
+
+void ClientSocket::UpdateConnectivityState(bool is_reused) {
+  // Record if this connection has every actually connected successfully.
+  // Note that IsConnected() won't be defined at destruction time, so we need
+  // to record this data now, while the derived class is present.
+  was_ever_connected_ |= IsConnected();
+  // A socket is_reused only after it has transmitted some data.
+  was_used_to_transmit_data_ |= is_reused;
+}
+
+}  // namespace net
+