Move Singleton and related structs to namespace base

extensions/browser/extension_function.cc

Index: extensions/browser/extension_function.cc
diff --git a/extensions/browser/extension_function.cc b/extensions/browser/extension_function.cc
index f9a7d3f0e59c2440e08642e2d775a9849e5bf55d..83747f89892e5974b5e2f0e48e0841a07042c950 100644
--- a/extensions/browser/extension_function.cc
+++ b/extensions/browser/extension_function.cc
@@ -141,7 +141,7 @@ class UserGestureForTests {
 
  private:
   UserGestureForTests();
-  friend struct DefaultSingletonTraits<UserGestureForTests>;
+  friend struct base::DefaultSingletonTraits<UserGestureForTests>;
 
   base::Lock lock_; // for protecting access to count_
   int count_;
@@ -149,7 +149,7 @@ class UserGestureForTests {
 
 // static
 UserGestureForTests* UserGestureForTests::GetInstance() {
-  return Singleton<UserGestureForTests>::get();
+  return base::Singleton<UserGestureForTests>::get();
 }
 
 UserGestureForTests::UserGestureForTests() : count_(0) {}