Support speculative pre-connection to search URLs

Implement several flavors of TCP/IP speculative preconnection
under a command line flag (not yet on by default).

The first area of preconnection takes place when a user types
a query into the omnibox, as we preconnect to the search service
when the omnibox suggests it is going to do a search.

The second area involves subresources, such as images.
When a navigation takes place, and we've seen navigations
to that domain/port before, and the history-based 
probabability that we'll need to make a connection to
a second site (host/port) is sufficiently large, then we
preconnect to that second site while we are still connecting
to the primary site (and before we've gotten content from
the primary site.

We also fall-back to mere DNS pre-resolution of subresource
hostnames when the probability of a connection to the
subresource is not high enough.

BUG=42694
r=pkasting,willchan,mbelshe
Review URL: http://codereview.chromium.org/1585029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@47479 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 4 insertions, 2 deletions

diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index a2860ac..c624a99 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -53,7 +53,8 @@ class IOThread : public BrowserProcessSubThread {
                      base::TimeDelta max_queue_delay,
                      size_t max_concurrent,
                      const chrome_common_net::NameList& hostnames_to_prefetch,
-                     ListValue* referral_list);
+                     ListValue* referral_list,
+                     bool preconnect_enabled);
 
   // Handles changing to On The Record mode.  Posts a task for this onto the
   // IOThread's message loop.
@@ -72,7 +73,8 @@ class IOThread : public BrowserProcessSubThread {
       base::TimeDelta max_queue_delay,
       size_t max_concurrent,
       chrome_common_net::NameList hostnames_to_prefetch,
-      ListValue* referral_list);
+      ListValue* referral_list,
+      bool preconnect_enabled);
 
   void ChangedToOnTheRecordOnIOThread();