Implement WebPrescientNetworking to trigger preconnect from Blink

chrome/browser/net/predictor.cc

Index: chrome/browser/net/predictor.cc
diff --git a/chrome/browser/net/predictor.cc b/chrome/browser/net/predictor.cc
index 3981c5e871bde70539efe9e5f546e3f72d7d9469..27dd4467005f906256ad26f96402285dd8cb0c4f 100644
--- a/chrome/browser/net/predictor.cc
+++ b/chrome/browser/net/predictor.cc
@@ -273,19 +273,27 @@ void Predictor::AnticipateOmniboxUrl(const GURL& url, bool preconnectable) {
                  CanonicalizeUrl(url), motivation));
 }
 
-void Predictor::PreconnectUrlAndSubresources(const GURL& url) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+void Predictor::PreconnectUrlAndSubresources(
+    const GURL& url,
+    UrlInfo::ResolutionMotivation motivation) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
+         BrowserThread::CurrentlyOn(BrowserThread::IO));
   if (!predictor_enabled_)
     return;
   if (!url.is_valid() || !url.has_host())
     return;
   if (preconnect_enabled()) {

[jar (doing other things), 2013/05/08 01:34:25]

nit: please do an early return here, when !preconnect_enabled() to make it
easier to read.

You could make a bigger list of || if you'd like now that we have 3 returns in a
row. (probably should have done this earlier... but your change helps make this
last if-clause large enough that I was having a hard time seeing matching
curlies).

[kouhei (in TOK), 2013/05/08 02:09:39]

Done. I love early returns.

     std::string host = url.HostNoBrackets();
-    UrlInfo::ResolutionMotivation motivation(UrlInfo::EARLY_LOAD_MOTIVATED);
     const int kConnectionsNeeded = 1;
-    PreconnectOnUIThread(CanonicalizeUrl(url), motivation,
-                         kConnectionsNeeded,
-                         url_request_context_getter_);
+    if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+      PreconnectOnUIThread(CanonicalizeUrl(url), motivation,
+                           kConnectionsNeeded,
+                           url_request_context_getter_);
+    } else {
+      PreconnectOnIOThread(CanonicalizeUrl(url), motivation,
+                           kConnectionsNeeded,
+                           url_request_context_getter_);
+    }
     PredictFrameSubresources(url.GetWithEmptyPath());
   }
 }