Move Singleton and related structs to namespace base

content/browser/tcmalloc_internals_request_job.cc

Index: content/browser/tcmalloc_internals_request_job.cc
diff --git a/content/browser/tcmalloc_internals_request_job.cc b/content/browser/tcmalloc_internals_request_job.cc
index 85ec2ed1c92268ad3e3603f97301fd60ad647ad5..e55df5e5141ac83d0ffe24fba06bcca3c92e18e4 100644
--- a/content/browser/tcmalloc_internals_request_job.cc
+++ b/content/browser/tcmalloc_internals_request_job.cc
@@ -16,7 +16,7 @@ namespace content {
 
 // static
 AboutTcmallocOutputs* AboutTcmallocOutputs::GetInstance() {
-  return Singleton<AboutTcmallocOutputs>::get();
+  return base::Singleton<AboutTcmallocOutputs>::get();
 }
 
 AboutTcmallocOutputs::AboutTcmallocOutputs() {}