Added chrome-side support for link rel=preconnect

chrome/browser/renderer_host/chrome_render_message_filter.cc

Index: chrome/browser/renderer_host/chrome_render_message_filter.cc
diff --git a/chrome/browser/renderer_host/chrome_render_message_filter.cc b/chrome/browser/renderer_host/chrome_render_message_filter.cc
index 18d11c8c0a2fc0b5759f3e6491dbd170bd1aa4c5..7c38c5090d0b7fc86bad3ed63ea7cf348cb928e7 100644
--- a/chrome/browser/renderer_host/chrome_render_message_filter.cc
+++ b/chrome/browser/renderer_host/chrome_render_message_filter.cc
@@ -45,7 +45,7 @@ namespace {
 
 const uint32 kFilteredMessageClasses[] = {
   ChromeMsgStart,
-  DnsPrefetchMsgStart,
+  NetworkHintsMsgStart,
 };
 
 }  // namespace
@@ -67,8 +67,8 @@ ChromeRenderMessageFilter::~ChromeRenderMessageFilter() {
 bool ChromeRenderMessageFilter::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(ChromeRenderMessageFilter, message)
-    IPC_MESSAGE_HANDLER(DnsPrefetchMsg_RequestPrefetch, OnDnsPrefetch)
-    IPC_MESSAGE_HANDLER(ChromeViewHostMsg_Preconnect, OnPreconnect)
+    IPC_MESSAGE_HANDLER(NetworkHintsMsg_DNSPrefetch, OnDnsPrefetch)
+    IPC_MESSAGE_HANDLER(NetworkHintsMsg_Preconnect, OnPreconnect)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_ResourceTypeStats,
                         OnResourceTypeStats)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_UpdatedCacheStats,
@@ -112,10 +112,16 @@ void ChromeRenderMessageFilter::OnDnsPrefetch(
     predictor_->DnsPrefetchList(request.hostname_list);
 }
 
-void ChromeRenderMessageFilter::OnPreconnect(const GURL& url) {
-  if (predictor_)
+void ChromeRenderMessageFilter::OnPreconnect(const GURL& url, int count) {
+  if (count < 1)
+    count = 1;

[Deprecated (see juliatuttle), 2015/02/10 17:48:42]

I'd discard the message (and maybe log a warning?) if count < 1. That shouldn't
happen, and it seems weird to silently fix it up.

[Pat Meenan, 2015/02/10 18:44:49]

Done.

+  else if (count > 6)

[Deprecated (see juliatuttle), 2015/02/10 17:48:42]

Make this a constant, or pull it from somewhere else (if it's e.g. some
connection limit set elsewhere)?

[mmenke, 2015/02/10 17:57:25]

Can we just preconnect however many are requested?  If we don't allow that many
preconnects, so what?  Doesn't seem like this should be the place we check.  The
socket pools already do this, anyways. 
https://code.google.com/p/chromium/codesearch#chromium/src/net/socket/client_...

[Pat Meenan, 2015/02/10 18:44:49]

Done.

+    count = 6;
+  if (predictor_ && url.is_valid() && url.has_host() && url.has_scheme() &&
+      url.SchemeIsHTTPOrHTTPS()) {
     predictor_->PreconnectUrl(
-        url, GURL(), chrome_browser_net::UrlInfo::MOUSE_OVER_MOTIVATED, 1);
+        url, GURL(), chrome_browser_net::UrlInfo::EARLY_LOAD_MOTIVATED, count);
+  }
 }
 
 void ChromeRenderMessageFilter::OnResourceTypeStats(