Added chrome-side support for link rel=preconnect

components/network_hints/renderer/renderer_preconnect.h

+// Copyright 2015 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.
+
+// A RendererPreconnect instance is maintained for each RenderThread.
+// URL strings are typically added to the embedded queue during rendering.
+// The first addition to the queue (transitioning from empty to having
+// some names) causes a processing task to be added to the Renderer Thread.
+// The processing task gathers all buffered URLs, and send them via IPC
+// to the browser.
+// This class counts repeated requests for the same URL and requests that
+// number of connections be preconnected. If multiple requests are sent
+// separately the net stack will just keep re-using the first pending
+// connection so we allow for the time between the parsing of the tags and
+// when the task is scheduled to accumulate multiple requests.
+
+#ifndef COMPONENTS_NETWORK_HINTS_RENDERER_RENDERER_PRECONNECT_H_
+#define COMPONENTS_NETWORK_HINTS_RENDERER_RENDERER_PRECONNECT_H_
+
+#include <map>
+
+#include "base/basictypes.h"
+#include "base/memory/weak_ptr.h"
+#include "url/gurl.h"
+
+namespace network_hints {
+
+// An internal interface to the network_hints component for efficiently sending
+// DNS prefetch requests to the net stack.
+class RendererPreconnect {
+ public:
+  RendererPreconnect();
+  ~RendererPreconnect();
+
+  // Push a name into the queue to be preconnected.
+  void Preconnect(const GURL &url);
+
+  // SubmitPreconnect processes the buffered URLs, and submits them for
+  // preconnecting.  Multiple requests for the same URL will increase the number
+  // of connections requested.
+  void SubmitPreconnect();
+
+ private:
+  // url_request_count_map_ contains (for each URL) a count for the number of
+  // times it was requested.
+  typedef std::map<GURL, int> UrlRequestCountMap;
+  UrlRequestCountMap url_request_count_map_;
+
+  base::WeakPtrFactory<RendererPreconnect> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(RendererPreconnect);
+};  // class RendererPreconnect
+
+}  // namespace network_hints
+
+#endif  // COMPONENTS_NETWORK_HINTS_RENDERER_RENDERER_PRECONNECT_H_