[mojo-edk] Simplify multiprocess pipe bootstrap

mojo/shell/runner/child/runner_connection.cc

Index: mojo/shell/runner/child/runner_connection.cc
diff --git a/mojo/shell/runner/child/runner_connection.cc b/mojo/shell/runner/child/runner_connection.cc
index 75b4648dc0db58f70f7753fe65959533d4e84baa..313c00a338d7bdade01b3a465639378835f78a0b 100644
--- a/mojo/shell/runner/child/runner_connection.cc
+++ b/mojo/shell/runner/child/runner_connection.cc
@@ -74,13 +74,6 @@ class Blocker {
 using GotApplicationRequestCallback =
     base::Callback<void(InterfaceRequest<mojom::ShellClient>)>;
 
-void OnCreateMessagePipe(ScopedMessagePipeHandle* result,
-                         Blocker::Unblocker unblocker,
-                         ScopedMessagePipeHandle pipe) {
-  *result = std::move(pipe);
-  unblocker.Unblock(base::Bind(&base::DoNothing));
-}
-
 void OnGotApplicationRequest(InterfaceRequest<mojom::ShellClient>* out_request,
                              InterfaceRequest<mojom::ShellClient> request) {
   *out_request = std::move(request);
@@ -229,14 +222,11 @@ bool RunnerConnectionImpl::WaitForApplicationRequest(
     std::string primordial_pipe_token =
         base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
             switches::kPrimordialPipeToken);
-    Blocker blocker;
-    edk::CreateChildMessagePipe(
-        primordial_pipe_token,
-        base::Bind(&OnCreateMessagePipe, base::Unretained(&handle),
-                   blocker.GetUnblocker()));
-    blocker.Block();
+    handle = edk::CreateChildMessagePipe(primordial_pipe_token);
   }
 
+  DCHECK(handle.is_valid());
+
   Blocker blocker;
   controller_runner_->PostTask(
       FROM_HERE,