Use ChannelMojo from the browser to NaCl loader process.

components/nacl/loader/nacl_helper_win_64.cc

Index: components/nacl/loader/nacl_helper_win_64.cc
diff --git a/components/nacl/loader/nacl_helper_win_64.cc b/components/nacl/loader/nacl_helper_win_64.cc
index 22cf61e3dad4ee40ccf3e054eee18838dce980ec..a17fe888a0a745637411c4949c973adff8e64c24 100644
--- a/components/nacl/loader/nacl_helper_win_64.cc
+++ b/components/nacl/loader/nacl_helper_win_64.cc
@@ -25,6 +25,9 @@
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "content/public/common/sandbox_init.h"
+#include "mojo/edk/embedder/embedder.h"
+#include "mojo/edk/embedder/platform_channel_pair.h"
+#include "mojo/edk/embedder/scoped_ipc_support.h"
 #include "sandbox/win/src/sandbox_types.h"
 
 extern int NaClMain(const content::MainFunctionParams&);
@@ -36,6 +39,14 @@ int NaClBrokerMain(const content::MainFunctionParams& parameters) {
   base::MessageLoopForIO main_message_loop;
   base::PlatformThread::SetName("CrNaClBrokerMain");
 
+  mojo::edk::Init();
+  mojo::edk::ScopedIPCSupport mojo_ipc_support(main_message_loop.task_runner());
+  mojo::edk::ScopedPlatformHandle platform_channel(
+      mojo::edk::PlatformChannelPair::PassClientHandleFromParentProcess(
+          *base::CommandLine::ForCurrentProcess()));
+  DCHECK(platform_channel.is_valid());
+  mojo::edk::SetParentPipeHandle(std::move(platform_channel));

[dcheng, 2016/09/21 05:18:33]

I'm a bit confused about this one as well. The documentation says:
  // Should be called as early as possible in the child process with the handle
  // that the parent received from ChildProcessLaunched.

But ChildProcessLaunched() doesn't appear to return anything or have any out
values.

[Sam McNally, 2016/09/21 07:49:46]

Previously, there was an overload of ChildProcessLaunched() that returned a
ScopedPlatformHandle to pass to the child instead of taking the parent end. That
comment seems to have been neglected.

From the mojo system's perspective, when launching a new process the embedder
needs to create a pipe (usually in the parent process) and pass one end to
ChildProcessLaunched() in the parent process and the other to
SetParentPipeHandle() in the child process. mojo::edk::PlatformChannelPair
provides an implementation of the pipe and passing one end to the child.

+
   std::unique_ptr<base::PowerMonitorSource> power_monitor_source(
       new base::PowerMonitorDeviceSource());
   base::PowerMonitor power_monitor(std::move(power_monitor_source));