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, 2 insertions, 2 deletions

diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 4d73e6a..b7dc105 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -164,8 +164,8 @@ const wchar_t kDnsPrefetchingEnabled[] = L"dns_prefetching.enabled";
 const wchar_t kDnsStartupPrefetchList[] = L"StartupDNSPrefetchList";
 
 // A list of host names used to fetch web pages, and their commonly used
-// sub-resource hostnames (and expected latency benefits from pre-resolving such
-// sub-resource hostnames).
+// sub-resource hostnames (and expected latency benefits from pre-resolving, or
+// preconnecting to, such sub-resource hostnames).
 // This list is adaptively grown and pruned.
 const wchar_t kDnsHostReferralList[] = L"HostReferralList";