Add a convenience typedef LazyInstance<T>::Leaky to avoid repeating T.

base/lazy_instance.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.
 
 // The LazyInstance<Type, Traits> class manages a single instance of Type,
 // which will be lazily created on the first time it's accessed.  This class is
 // useful for places you would normally use a function-level static, but you
 // need to have guaranteed thread-safety.  The Type constructor will only ever
 // be called once, even if two threads are racing to create the object.  Get()
 // and Pointer() will always return the same, completely initialized instance.
@@ skipping 55 matching lines @@
     // Use placement new to initialize our instance in our preallocated space.
     // The parenthesis is very important here to force POD type initialization.
     return new (instance) Type();
   }
   static void Delete(Type* instance) {
     // Explicitly call the destructor.
     instance->~Type();
   }
 };
 
+// Use LazyInstance<T>::Leaky for a less-verbose call-site typedef.

[wtc, 2012/01/21 00:51:01]

Nit: would be nice to give an example.  Before I saw your
change to base/lazy_instance_unittest.cc, I didn't understand
this comment completely.

Nit: Is it possible for this convenience typedef to be
named LeakyLazyInstance<T>?

[Ami GONE FROM CHROMIUM, 2012/01/21 01:22:30]

Done.
Not until we adopt c++11 and get template typedefs.
I tried being tricksy with subclassing, but that breaks brace initialization.

 template <typename Type>
 struct LeakyLazyInstanceTraits {
   static const bool kRegisterOnExit = false;
   static const bool kAllowedToAccessOnNonjoinableThread = true;
 
   static Type* New(void* instance) {
     return DefaultLazyInstanceTraits<Type>::New(instance);
   }
   static void Delete(Type* instance) {
   }
@@ skipping 24 matching lines @@
 template <typename Type, typename Traits = DefaultLazyInstanceTraits<Type> >
 class LazyInstance {
  public:
   // Do not define a destructor, as doing so makes LazyInstance a
   // non-POD-struct. We don't want that because then a static initializer will
   // be created to register the (empty) destructor with atexit() under MSVC, for
   // example. We handle destruction of the contained Type class explicitly via
   // the OnExit member function, where needed.
   // ~LazyInstance() {}
 
+  // Convenience typedef to avoid having to repeat Type for leaky lazy
+  // instances.
+  typedef LazyInstance<Type, LeakyLazyInstanceTraits<Type> > Leaky;
+
   Type& Get() {
     return *Pointer();
   }
 
   Type* Pointer() {
 #ifndef NDEBUG
     // Avoid making TLS lookup on release builds.
     if (!Traits::kAllowedToAccessOnNonjoinableThread)
       ThreadRestrictions::AssertSingletonAllowed();
 #endif
@@ skipping 59 matching lines @@
     LazyInstance<Type, Traits>* me =
         reinterpret_cast<LazyInstance<Type, Traits>*>(lazy_instance);
     Traits::Delete(me->instance());
     subtle::Release_Store(&me->private_instance_, 0);
   }
 };
 
 }  // namespace base
 
 #endif  // BASE_LAZY_INSTANCE_H_