Adds the ability for the renderer to create the mojo channel

content/common/mojo/mojo_channel_init.cc

+// Copyright (c) 2014 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/common/mojo/mojo_channel_init.h"
+
+#include "base/bind.h"
+#include "base/lazy_instance.h"
+#include "base/message_loop/message_loop.h"
+#include "base/synchronization/lock.h"
+#include "mojo/system/embedder/embedder.h"
+
+namespace content {
+
+namespace {
+
+// Initializes mojo. Use a lock to ensure we only do this once.
+// TODO(sky): this likely wants to move to a more central location, such as
+// startup.
+void InitMojo() {
+  static base::LazyInstance<base::Lock> lock = LAZY_INSTANCE_INITIALIZER;

[darin (slow to review), 2014/03/14 22:03:36]

hmm, to be we don't have an equivalent of pthread_once(). perhaps an alternative
is:

struct Initializer {
  Initializer() {
    mojo::embedder::Init();
  }
};
static base::lazyInstance<Initializer>::Leaky initializer =
    LAZY_INSTANCE_INITIALIZER;

void InitMojo() {
  initializer.Get();
}

I'm not sure if it matters, but it saves you from needing to allocate a lock.
This just relies on the LazyInstance to run the constructor exactly once. (This
does not result in malloc being called.)

I agree it would probably be good to move this function to some earlier part of
startup when we know we only have one thread active.

[sky, 2014/03/14 22:45:12]

Done.

+  static bool inited = false;
+  base::AutoLock auto_lock(lock.Get());
+  if (!inited) {
+    inited = true;
+    mojo::embedder::Init();
+  }
+}
+
+}  // namespace
+
+MojoChannelInit::MojoChannelInit()
+    : main_thread_(base::MessageLoop::current()->message_loop_proxy()),
+      channel_info_(NULL),
+      weak_factory_(this) {
+}
+
+MojoChannelInit::~MojoChannelInit() {
+  bootstrap_message_pipe_.reset();
+  if (channel_info_) {
+    io_thread_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&mojo::embedder::DestroyChannelOnIOThread, channel_info_));
+  }
+}
+
+void MojoChannelInit::Init(
+    base::PlatformFile file,
+    scoped_refptr<base::TaskRunner> io_thread_task_runner) {
+  DCHECK(!io_thread_task_runner_.get());  // Should only init once.
+  io_thread_task_runner_ = io_thread_task_runner;
+  InitMojo();
+  bootstrap_message_pipe_.reset(
+      mojo::Handle(
+          mojo::embedder::CreateChannel(
+              mojo::embedder::ScopedPlatformHandle(
+                  mojo::embedder::PlatformHandle(file)),
+              io_thread_task_runner,
+              base::Bind(&MojoChannelInit::OnCreatedChannelOnIOThread,
+                         weak_factory_.GetWeakPtr(),
+                         main_thread_,
+                         io_thread_task_runner))));
+}
+
+// static
+void MojoChannelInit::OnCreatedChannelOnIOThread(
+    base::WeakPtr<MojoChannelInit> host,
+    scoped_refptr<base::TaskRunner> main_thread,
+    scoped_refptr<base::TaskRunner> io_thread,
+    mojo::embedder::ChannelInfo* channel) {
+  main_thread->PostTask(
+      FROM_HERE,
+      base::Bind(&MojoChannelInit::OnCreatedChannelOnMainThread, host,
+                 io_thread, channel));
+}
+
+// static
+void MojoChannelInit::OnCreatedChannelOnMainThread(
+    base::WeakPtr<MojoChannelInit> host,
+    scoped_refptr<base::TaskRunner> io_thread,
+    mojo::embedder::ChannelInfo* channel) {
+  // By the time we get here |host| may have been destroyed. If so, shutdown the
+  // channel.
+  if (!host.get()) {
+    io_thread->PostTask(
+        FROM_HERE,
+        base::Bind(&mojo::embedder::DestroyChannelOnIOThread, channel));
+    return;
+  }
+  host->channel_info_ = channel;
+}
+
+
+}  // namespace content