Move Singleton and related structs to namespace base

chrome/browser/net/utility_process_mojo_proxy_resolver_factory.cc

Index: chrome/browser/net/utility_process_mojo_proxy_resolver_factory.cc
diff --git a/chrome/browser/net/utility_process_mojo_proxy_resolver_factory.cc b/chrome/browser/net/utility_process_mojo_proxy_resolver_factory.cc
index 4c4e888ebaa0b7e7494c08d98af79a6891be6161..fda8201417ad6946d86b213ffd446d53142bebe9 100644
--- a/chrome/browser/net/utility_process_mojo_proxy_resolver_factory.cc
+++ b/chrome/browser/net/utility_process_mojo_proxy_resolver_factory.cc
@@ -23,9 +23,9 @@ const int kUtilityProcessIdleTimeoutSeconds = 5;
 UtilityProcessMojoProxyResolverFactory*
 UtilityProcessMojoProxyResolverFactory::GetInstance() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
-  return Singleton<
-      UtilityProcessMojoProxyResolverFactory,
-      LeakySingletonTraits<UtilityProcessMojoProxyResolverFactory>>::get();
+  return base::Singleton<UtilityProcessMojoProxyResolverFactory,
+                         base::LeakySingletonTraits<
+                             UtilityProcessMojoProxyResolverFactory>>::get();
 }
 
 UtilityProcessMojoProxyResolverFactory::