Declarative resource hints go through mojo IPC to //content

content/browser/loader/resource_hints_controller.h

+// Copyright 2016 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.
+
+#ifndef CONTENT_BROWSER_LOADER_RESOURCE_HINTS_CONTROLLER_H_
+#define CONTENT_BROWSER_LOADER_RESOURCE_HINTS_CONTROLLER_H_
+
+#include "base/macros.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+#include "third_party/WebKit/public/platform/resource_hints.mojom.h"
+#include "url/gurl.h"
+
+namespace content {
+
+class RenderProcessHost;
+class ResourceContext;
+
+// Listeners for resource hints requests from a frame in the render process.
+class ResourceHintsController : public blink::mojom::ResourceHintsHandler {

[kinuko, 2016/06/16 05:39:58]

nit: the most common naming pattern seems to be to name it like 
MojoInterfaceNameImpl, e.g. ResourceHintsHandlerImpl, which might make this file
more findable for others

[Charlie Harrison, 2016/06/16 11:00:20]

Done.

+ public:
+  // |controller| and |resource_context| must outlive this class.
+  ResourceHintsController(blink::mojom::ResourceHintsHandlerRequest request,
+                          ResourceContext* resource_context);
+
+  ~ResourceHintsController() override;
+
+  // blink::mojom::ResourceHintsHandler:
+  void Preresolve(const GURL& url) override;
+  void Preconnect(const GURL& url,
+                  bool credentials_flag,
+                  uint8_t num_connections) override;
+
+  static void RegisterConnection(
+      RenderProcessHost* render_process_host,
+      blink::mojom::ResourceHintsHandlerRequest request);
+
+ private:
+  static void RegisterConnectionOnIOThread(
+      ResourceContext* resource_context,
+      blink::mojom::ResourceHintsHandlerRequest request);
+  ResourceContext* resource_context_;
+  mojo::StrongBinding<blink::mojom::ResourceHintsHandler> binding_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResourceHintsController);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_RESOURCE_HINTS_CONTROLLER_H_