Implement WebPrescientNetworking to trigger preconnect from Blink

chrome/browser/net/predictor.cc

 // Copyright (c) 2012 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 "chrome/browser/net/predictor.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 #include <sstream>
@@ skipping 255 matching lines @@
   last_omnibox_preresolve_ = now;
 
   // Perform at least DNS pre-resolution.
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&Predictor::Resolve, base::Unretained(this),
                  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());
   }
 }
 
 UrlList Predictor::GetPredictedUrlListAtStartup(
     PrefService* user_prefs,
     PrefService* local_state) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   UrlList urls;
   // Recall list of URLs we learned about during last session.
@@ skipping 887 matching lines @@
     IOThread* io_thread,
     net::URLRequestContextGetter* getter) {
   // Empty function for unittests.
 }
 
 void SimplePredictor::ShutdownOnUIThread(PrefService* user_prefs) {
   SetShutdown(true);
 }
 
 }  // namespace chrome_browser_net