Move runner stuff into a runner namespace.

mojo/runner/task_runners.cc

Index: mojo/runner/task_runners.cc
diff --git a/mojo/runner/task_runners.cc b/mojo/runner/task_runners.cc
index e4a49d657431a201744765d79f6bdebed120d1f6..c69f7c48867eee036e98b50c618f943d9eaff24a 100644
--- a/mojo/runner/task_runners.cc
+++ b/mojo/runner/task_runners.cc
@@ -7,7 +7,7 @@
 #include "base/threading/sequenced_worker_pool.h"
 
 namespace mojo {
-namespace shell {
+namespace runner {
 
 namespace {
 
@@ -35,5 +35,5 @@ TaskRunners::~TaskRunners() {
   blocking_pool_->Shutdown();
 }
 
-}  // namespace shell
+}  // namespace runner
 }  // namespace mojo