Declarative resource hints go through mojo IPC to //content

content/browser/loader/resource_hints_controller.cc

+// 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.
+
+#include "content/browser/loader/resource_hints_controller.h"
+
+#include "base/memory/ptr_util.h"
+#include "content/browser/loader/resource_dispatcher_host_impl.h"
+#include "content/public/browser/browser_context.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/resource_context.h"
+#include "content/public/browser/resource_dispatcher_host_delegate.h"
+#include "content/public/browser/resource_hints.h"
+#include "net/base/address_list.h"
+#include "net/dns/host_resolver.h"
+#include "net/dns/single_request_host_resolver.h"
+#include "net/url_request/url_request_context.h"
+
+namespace content {
+
+// static
+void ResourceHintsController::RegisterConnection(
+    RenderProcessHost* render_process_host,
+    mojo::InterfaceRequest<blink::mojom::ResourceHintsDispatcherHost> request) {

[yzshen1, 2016/06/08 17:40:53]

nit: in case you don't know, you can use a shorter name
blink::mojom::ResourceHintsDispatcherHostRequest

[Charlie Harrison, 2016/06/10 14:20:00]

Thank you :) done.

+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(&ResourceHintsController::RegisterConnectionOnIOThread,
+                 render_process_host->GetBrowserContext()->GetResourceContext(),

[yzshen1, 2016/06/08 17:40:53]

Is it guaranteed that resource context outlives this post task and also the
resulted controller?

[Charlie Harrison, 2016/06/10 14:20:00]

I'm unsure. What are the semantics of the channel's lifetime? The
ResourceContext will be destroyed when the IO thread is terminated
(~ProfileIOData, specifically). I chatted with mmenke@ who told me that
ProfileIOData will be deleted after WebContents/RenderFrame. If the strong
binding deletes us at that time I think we're good.

[yzshen1, 2016/06/10 15:45:43]

If the renderer doesn't disconnect earlier, the strong binding will get a
connection error notification (and therefore delete us) from a message loop
destruction observer, i.e., in the MessageLoop destructor.

I don't know much as the life time of ResourceContext.

+                 base::Passed(&request)));
+}
+
+// static
+void ResourceHintsController::RegisterConnectionOnIOThread(
+    ResourceContext* resource_context,
+    mojo::InterfaceRequest<blink::mojom::ResourceHintsDispatcherHost> request) {
+  // Will be deleted when the connection goes away.
+  new ResourceHintsController(std::move(request), resource_context);
+}
+
+ResourceHintsController::ResourceHintsController(
+    mojo::InterfaceRequest<blink::mojom::ResourceHintsDispatcherHost> request,
+    ResourceContext* resource_context)
+    : resource_context_(resource_context), binding_(this, std::move(request)) {
+  binding_.set_connection_error_handler(
+      base::Bind(&ResourceHintsController::HostHadConnectionError,
+                 base::Unretained(this)));
+}
+
+ResourceHintsController::~ResourceHintsController() {}
+
+void ResourceHintsController::HostHadConnectionError() {
+  delete this;

[yzshen1, 2016/06/08 17:40:53]

Please take a look at strong_binding.h.

It does this for you.

[kinuko, 2016/06/09 07:09:19]

Yeah we shouldn't need this.

[Charlie Harrison, 2016/06/10 14:20:00]

Done. Thanks for the pointer.

+}
+
+void ResourceHintsController::DispatchPreresolve(const GURL& url) {
+  PreresolveUrl(resource_context_, url, net::CompletionCallback());
+}
+
+void ResourceHintsController::DispatchPreconnect(const GURL& url,
+                                                 bool credentials_flag,
+                                                 uint8_t num_connections) {
+  // TODO(csharrison): Remove HttpRequestInfo::RequestMotivation and add a
+  // better enum at the //content layer.
+  PreconnectUrl(resource_context_, url, GURL(), num_connections,
+                credentials_flag, net::HttpRequestInfo::EARLY_LOAD_MOTIVATED);
+}
+
+}  // namespace content