**NOTFORLANDING** New link rel=prerender API

chrome/browser/prerender/prerender_message_filter.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/prerender/prerender_message_filter.h"
+
+#include "base/bind.h"
+#include "chrome/browser/prerender/prerender_link_manager.h"
+#include "chrome/browser/prerender/prerender_link_manager_factory.h"
+#include "chrome/common/prerender_messages.h"
+#include "content/public/browser/browser_thread.h"
+
+using content::BrowserThread;
+
+namespace {
+
+void OnChannelClosingInUIThread(Profile* profile, int render_process_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  prerender::PrerenderLinkManager* prerender_link_manager =
+      prerender::PrerenderLinkManagerFactory::GetForProfile(profile);
+  if (!prerender_link_manager)
+    return;
+  prerender_link_manager->OnChannelClosing(render_process_id);
+}
+
+}
+
+namespace prerender {
+
+PrerenderMessageFilter::PrerenderMessageFilter(int render_process_id,
+                                               Profile* profile)
+    : render_process_id_(render_process_id),
+      profile_(profile)
+{

[cbentzel, 2012/04/24 15:42:59]

Nit: move this up with profile_

[gavinp, 2012/04/26 23:55:39]

Done.

NitFromMeToTheUniverse: WebKit and chrome have different style guides on this!

+}
+
+bool PrerenderMessageFilter::OnMessageReceived(const IPC::Message& message,
+                                               bool* message_was_ok) {
+  bool handled = true;
+  IPC_BEGIN_MESSAGE_MAP_EX(PrerenderMessageFilter, message, *message_was_ok)
+    IPC_MESSAGE_HANDLER(PrerenderHostMsg_AddPrerender, OnAddPrerender)
+    IPC_MESSAGE_HANDLER(PrerenderHostMsg_CancelPrerender, OnCancelPrerender)
+    IPC_MESSAGE_HANDLER(PrerenderHostMsg_AbandonPrerender, OnAbandonPrerender)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+
+  return handled;
+}
+
+void PrerenderMessageFilter::OverrideThreadForMessage(
+    const IPC::Message& message, content::BrowserThread::ID* thread) {
+  if (message.type() == PrerenderHostMsg_AddPrerender::ID ||

[cbentzel, 2012/04/24 15:42:59]

What are the lifetime guarantees for both PrerenderMessageFilter and profile_
when these are handled on the UI thread? For example, is it possible for the
profile_ to be destroyed between when OnChannelClosing is called on IO thread
and OnChannelClosingInUIThread is invoked on UI thread?

[gavinp, 2012/04/26 23:55:39]

At creation, the PrerenderMessageFilter is placed on the IPC::ChannelProxy, and
that occurs on the UI thread.  The scope of that proxy should be the life of the
channel.  However, in the channel closing case, I don't know if it's legitimate,
as I'm posting my own task to another thread.  In the case of the other
messages, they should be good, since the PrerenderMessageFilter should be scoped
inside of the ChannelProxy which itself should be scoped inside of the
RendererProcessHost.

So in the OnChannelClosingInUIThread case, I believe I need to call
g_browser_process->profile_manager()->IsValidProfile(....), but I think I'm fine
in the other cases for the reason stated.  Who should we ask to double check
this logic for us?

+      message.type() == PrerenderHostMsg_CancelPrerender::ID ||
+      message.type() == PrerenderHostMsg_AbandonPrerender::ID) {
+    *thread = BrowserThread::UI;
+  }
+}
+
+void PrerenderMessageFilter::OnAddPrerender(
+    int prerender_id,
+    const GURL& url,
+    const content::Referrer& referrer,
+    const gfx::Size& size,
+    int render_view_route_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  PrerenderLinkManager* prerender_link_manager =
+      PrerenderLinkManagerFactory::GetForProfile(profile_);
+  if (!prerender_link_manager)
+    return;
+  prerender_link_manager->OnAddPrerender(
+      prerender_id, render_process_id_,
+      url, referrer, size, render_view_route_id);
+}
+
+void PrerenderMessageFilter::OnCancelPrerender(
+    int prerender_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  PrerenderLinkManager* prerender_link_manager =
+      PrerenderLinkManagerFactory::GetForProfile(profile_);
+  if (!prerender_link_manager)
+    return;
+  prerender_link_manager->OnCancelPrerender(
+      prerender_id, render_process_id_);
+}
+
+void PrerenderMessageFilter::OnAbandonPrerender(
+    int prerender_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  PrerenderLinkManager* prerender_link_manager =
+      PrerenderLinkManagerFactory::GetForProfile(profile_);
+  if (!prerender_link_manager)
+    return;
+  prerender_link_manager->OnAbandonPrerender(
+      prerender_id, render_process_id_);
+}
+
+void PrerenderMessageFilter::OnChannelClosing() {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&OnChannelClosingInUIThread, profile_, render_process_id_));
+}
+
+}