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 256 matching lines @@
 
   // 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));
-  if (!predictor_enabled_)
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
+         BrowserThread::CurrentlyOn(BrowserThread::IO));
+  if (!predictor_enabled_ || !preconnect_enabled() ||
+      !url.is_valid() || !url.has_host())
     return;
-  if (!url.is_valid() || !url.has_host())
-    return;
-  if (preconnect_enabled()) {
-    std::string host = url.HostNoBrackets();
-    UrlInfo::ResolutionMotivation motivation(UrlInfo::EARLY_LOAD_MOTIVATED);
-    const int kConnectionsNeeded = 1;
+
+  std::string host = url.HostNoBrackets();
+  UrlInfo::ResolutionMotivation motivation(UrlInfo::EARLY_LOAD_MOTIVATED);
+  const int kConnectionsNeeded = 1;
+  if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
     PreconnectOnUIThread(CanonicalizeUrl(url), motivation,
                          kConnectionsNeeded,
                          url_request_context_getter_);
-    PredictFrameSubresources(url.GetWithEmptyPath());
+  } 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.
   // This may catch secondary hostnames, pulled in by the homepages.  It will
   // also catch more of the "primary" home pages, since that was (presumably)
@@ skipping 885 matching lines @@
     IOThread* io_thread,
     net::URLRequestContextGetter* getter) {
   // Empty function for unittests.
 }
 
 void SimplePredictor::ShutdownOnUIThread(PrefService* user_prefs) {
   SetShutdown(true);
 }
 
 }  // namespace chrome_browser_net