Plumb explicit IPC task runner through to IPC::Channel creation

ipc/ipc_channel_factory.cc

Index: ipc/ipc_channel_factory.cc
diff --git a/ipc/ipc_channel_factory.cc b/ipc/ipc_channel_factory.cc
index dbb24c087e0cdf6cfe16b4a438bf14dd7175b690..8fb4d772e0072c8186cc6635bda73593af4c0d74 100644
--- a/ipc/ipc_channel_factory.cc
+++ b/ipc/ipc_channel_factory.cc
@@ -13,8 +13,11 @@ namespace {
 
 class PlatformChannelFactory : public ChannelFactory {
  public:
-  PlatformChannelFactory(ChannelHandle handle, Channel::Mode mode)
-      : handle_(handle), mode_(mode) {}
+  PlatformChannelFactory(
+      ChannelHandle handle,
+      Channel::Mode mode,
+      const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner)
+      : handle_(handle), mode_(mode), ipc_task_runner_(ipc_task_runner) {}
 
   std::string GetName() const override {
     return handle_.name;
@@ -23,14 +26,20 @@ class PlatformChannelFactory : public ChannelFactory {
   std::unique_ptr<Channel> BuildChannel(Listener* listener) override {
     if (handle_.mojo_handle.is_valid()) {
       return ChannelMojo::Create(
-          mojo::ScopedMessagePipeHandle(handle_.mojo_handle), mode_, listener);
+          mojo::ScopedMessagePipeHandle(handle_.mojo_handle), mode_, listener,
+          ipc_task_runner_);
     }
     return Channel::Create(handle_, mode_, listener);
   }
 
+  scoped_refptr<base::SingleThreadTaskRunner> GetIPCTaskRunner() override {
+    return ipc_task_runner_;
+  }
+
  private:
   ChannelHandle handle_;
   Channel::Mode mode_;
+  scoped_refptr<base::SingleThreadTaskRunner> ipc_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformChannelFactory);
 };
@@ -40,8 +49,10 @@ class PlatformChannelFactory : public ChannelFactory {
 // static
 std::unique_ptr<ChannelFactory> ChannelFactory::Create(
     const ChannelHandle& handle,
-    Channel::Mode mode) {
-  return base::WrapUnique(new PlatformChannelFactory(handle, mode));
+    Channel::Mode mode,
+    const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner) {
+  return base::WrapUnique(
+      new PlatformChannelFactory(handle, mode, ipc_task_runner));
 }
 
 }  // namespace IPC