Move Singleton and related structs to namespace base

chrome/browser/chromeos/device_uma.h

Index: chrome/browser/chromeos/device_uma.h
diff --git a/chrome/browser/chromeos/device_uma.h b/chrome/browser/chromeos/device_uma.h
index e26d41a982f845a44b355a6b0734002b6f59dc62..d6c16d6c6094209e78a9e3463d42c4fac0d86580 100644
--- a/chrome/browser/chromeos/device_uma.h
+++ b/chrome/browser/chromeos/device_uma.h
@@ -8,7 +8,9 @@
 #include "base/basictypes.h"
 #include "ui/events/platform/platform_event_observer.h"
 
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 namespace chromeos {
 
@@ -22,7 +24,7 @@ class DeviceUMA : public ui::PlatformEventObserver {
   void Stop();
 
  private:
-  friend struct DefaultSingletonTraits<DeviceUMA>;
+  friend struct base::DefaultSingletonTraits<DeviceUMA>;
 
   DeviceUMA();
   ~DeviceUMA() override;