Get rid of ChannelInit::SetSingleProcessIOTaskRunner()

The globally-set TaskRunner doesn't work because some child
thread can run inside the browser process even when other
child threads run in their own processes.
For example, there is a configuration where GpuChildThread
being in-process while RenderThreadImpl isn't.

It is troublesome once non-renderer child processes adopt
ChannelMojo.

This CL eliminates the global in-process IO task runner
and instead, passes an IO runnner for each thread
if it is configured as an in-process mode.

Note that InProcessChildThreadParams object is introuced to
clarify that the parameter is for in-process mode.

This is a spin-off from https://codereview.chromium.org/960693003/.

R=jamesr@chromium.org, rockot@chromium.org, jam@chromium.org
BUG=377980

Review URL: https://codereview.chromium.org/987693005

Cr-Commit-Position: refs/heads/master@{#321047}

2 files changed, 13 insertions, 9 deletions

diff --git a/content/child/mojo/mojo_application.cc b/content/child/mojo/mojo_application.cc
index f896dc6..5deee5d 100644
--- a/content/child/mojo/mojo_application.cc
+++ b/content/child/mojo/mojo_application.cc
@@ -13,7 +13,10 @@
 
 namespace content {
 
-MojoApplication::MojoApplication() {
+MojoApplication::MojoApplication(
+    scoped_refptr<base::SequencedTaskRunner> io_task_runner)
+    : io_task_runner_(io_task_runner) {
+  DCHECK(io_task_runner_);
 }
 
 MojoApplication::~MojoApplication() {
@@ -35,15 +38,9 @@ void MojoApplication::OnActivate(
 #elif defined(OS_WIN)
   base::PlatformFile handle = file;
 #endif
-  scoped_refptr<base::TaskRunner> io_task_runner =
-      ChannelInit::GetSingleProcessIOTaskRunner();
-  if (!io_task_runner) {
-    io_task_runner = ChildProcess::current()->io_message_loop_proxy();
-  }
-  DCHECK(io_task_runner);
 
   mojo::ScopedMessagePipeHandle message_pipe =
-      channel_init_.Init(handle, io_task_runner);
+      channel_init_.Init(handle, io_task_runner_);
   DCHECK(message_pipe.is_valid());
 
   ApplicationSetupPtr application_setup;
diff --git a/content/child/mojo/mojo_application.h b/content/child/mojo/mojo_application.h
index 5b89ddb..5c207f2 100644
--- a/content/child/mojo/mojo_application.h
+++ b/content/child/mojo/mojo_application.h
@@ -9,6 +9,10 @@
 #include "content/common/mojo/service_registry_impl.h"
 #include "ipc/ipc_platform_file.h"
 
+namespace base {
+class SequencedTaskRunner;
+}
+
 namespace IPC {
 class Message;
 }
@@ -21,7 +25,8 @@ namespace content {
 // It makes the ServiceRegistry interface available.
 class MojoApplication {
  public:
-  MojoApplication();
+  explicit MojoApplication(
+      scoped_refptr<base::SequencedTaskRunner> io_task_runner);
   virtual ~MojoApplication();
 
   bool OnMessageReceived(const IPC::Message& msg);
@@ -31,6 +36,8 @@ class MojoApplication {
  private:
   void OnActivate(const IPC::PlatformFileForTransit& file);
 
+  scoped_refptr<base::SequencedTaskRunner> io_task_runner_;
+
   ChannelInit channel_init_;
 
   ServiceRegistryImpl service_registry_;