Add the beginning of a simple window manager that we'll support on Windows.

services/service_manager/standalone/context.cc

Index: services/service_manager/standalone/context.cc
diff --git a/services/service_manager/standalone/context.cc b/services/service_manager/standalone/context.cc
index 93a48f5faca52121521ea93769aaff3e3b2dbd90..4aa11e3fec6154fe4f843260560e47311e911476 100644
--- a/services/service_manager/standalone/context.cc
+++ b/services/service_manager/standalone/context.cc
@@ -128,6 +128,7 @@ void Context::Init(std::unique_ptr<InitParams> init_params) {
     EnsureEmbedderIsInitialized();
 
   service_manager_runner_ = base::ThreadTaskRunnerHandle::Get();
+  base::SequencedWorkerPool::EnableForProcess();
   blocking_pool_ =
       new base::SequencedWorkerPool(kMaxBlockingPoolThreads, "blocking_pool",
                                     base::TaskPriority::USER_VISIBLE);