Add TaskPriority as a parameter to SequencedWorkerPool in preparation for TaskScheduler experiment.

services/shell/standalone/context.cc

 // Copyright 2013 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 "services/shell/standalone/context.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 119 matching lines @@
     tracer_.Start(
         command_line.GetSwitchValueASCII(::switches::kTraceStartup),
         command_line.GetSwitchValueASCII(::switches::kTraceStartupDuration),
         "mojo_runner.trace");
   }
 
   if (!init_params || init_params->init_edk)
     EnsureEmbedderIsInitialized();
 
   shell_runner_ = base::ThreadTaskRunnerHandle::Get();
-  blocking_pool_ =
-      new base::SequencedWorkerPool(kMaxBlockingPoolThreads, "blocking_pool");
+  blocking_pool_ = new base::SequencedWorkerPool(
+      kMaxBlockingPoolThreads, "blocking_pool", base::TaskPriority::BACKGROUND);

[jam, 2016/06/22 20:17:37]

similarly, i don't think this should be priority. when the mojo shell is reading
manifests (note, this isn't in production at the moment), it's blocked on
loading apps' manifest.

[gab, 2016/06/22 21:08:56]

Okay then everything but reading manifests should be BACKGROUND? And by virtue
of the comment in the CL description we have to take the maximum priority of all
potential tasks for now (until they are split in multiple task runners instead
of associated to a single pool).

So USER_VISIBLE?

 
   init_edk_ = !init_params || init_params->init_edk;
   if (init_edk_) {
     mojo::edk::InitIPCSupport(this, io_thread_->task_runner().get());
 #if defined(OS_MACOSX)
     mojo::edk::SetMachPortProvider(MachBroker::GetInstance()->port_provider());
 #endif
   }
 
   std::unique_ptr<NativeRunnerFactory> runner_factory;
@@ skipping 103 matching lines @@
 
   std::unique_ptr<ConnectParams> params(new ConnectParams);
   params->set_source(CreateShellIdentity());
   params->set_target(Identity(name, mojom::kRootUserID));
   params->set_remote_interfaces(mojo::GetProxy(&remote_interfaces));
   params->set_local_interfaces(std::move(local_interfaces));
   shell_->Connect(std::move(params));
 }
 
 }  // namespace shell