Add trace code to track all posted tasks in message_loop.

base/memory/singleton.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // PLEASE READ: Do you really need a singleton?
 //
 // Singletons make it hard to determine the lifetime of an object, which can
 // lead to buggy code and spurious crashes.
 //
 // Instead of adding another singleton into the mix, try to identify either:
@@ skipping 187 matching lines @@
 //
 template <typename Type,
           typename Traits = DefaultSingletonTraits<Type>,
           typename DifferentiatingType = Type>
 class Singleton {
  private:
   // Classes using the Singleton<T> pattern should declare a GetInstance()
   // method and call Singleton::get() from within that.
   friend Type* Type::GetInstance();
 
+  // Allow TraceLog tests to test tracing after OnExit.
+  friend class DeleteTraceLogForTesting;
+
   // This class is safe to be constructed and copy-constructed since it has no
   // member.
 
   // Return a pointer to the one true instance of the class.
   static Type* get() {
     if (!Traits::kAllowedToAccessOnNonjoinableThread)
       base::ThreadRestrictions::AssertSingletonAllowed();
 
     // Our AtomicWord doubles as a spinlock, where a value of
     // kBeingCreatedMarker means the spinlock is being held for creation.
@@ skipping 58 matching lines @@
     instance_ = 0;
   }
   static base::subtle::AtomicWord instance_;
 };
 
 template <typename Type, typename Traits, typename DifferentiatingType>
 base::subtle::AtomicWord Singleton<Type, Traits, DifferentiatingType>::
     instance_ = 0;
 
 #endif  // BASE_MEMORY_SINGLETON_H_