Move Singleton and related structs to namespace base

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index 4e7615f78f5ae9c416797fbfbd6ef3ee4e1b1866..57e38bdf315fa26c64bb35712837c92b433ef5e4 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -114,7 +114,7 @@ class MemoryUsageCache {
  public:
   // Retrieves the Singleton.
   static MemoryUsageCache* GetInstance() {
-    return Singleton<MemoryUsageCache>::get();
+    return base::Singleton<MemoryUsageCache>::get();
   }
 
   MemoryUsageCache() : memory_value_(0) { Init(); }