Move Singleton and related structs to namespace base

ppapi/proxy/ppb_image_data_proxy.cc

Index: ppapi/proxy/ppb_image_data_proxy.cc
diff --git a/ppapi/proxy/ppb_image_data_proxy.cc b/ppapi/proxy/ppb_image_data_proxy.cc
index 02fdad6f7ef9b25b512042b40eab7d4d9121f445..ed15bb6a1172afa4bd1c51bbc50593e6469b074c 100644
--- a/ppapi/proxy/ppb_image_data_proxy.cc
+++ b/ppapi/proxy/ppb_image_data_proxy.cc
@@ -244,7 +244,7 @@ class ImageDataCache {
   void DidDeleteInstance(PP_Instance instance);
 
  private:
-  friend struct LeakySingletonTraits<ImageDataCache>;
+  friend struct base::LeakySingletonTraits<ImageDataCache>;
 
   // Timer callback to expire entries for the given instance.
   void OnTimer(PP_Instance instance);
@@ -263,8 +263,8 @@ class ImageDataCache {
 
 // static
 ImageDataCache* ImageDataCache::GetInstance() {
-  return Singleton<ImageDataCache,
-                   LeakySingletonTraits<ImageDataCache> >::get();
+  return base::Singleton<ImageDataCache,
+                         base::LeakySingletonTraits<ImageDataCache>>::get();
 }
 
 scoped_refptr<ImageData> ImageDataCache::Get(