Reland 66791 (change was innocent)...

base/lazy_instance.h

 // Copyright (c) 2008 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 18 matching lines @@
 //     my_instance.Get().SomeMethod();  // MyClass::SomeMethod()
 //
 //     MyClass* ptr = my_instance.Pointer();
 //     ptr->DoDoDo();  // MyClass::DoDoDo
 //   }
 
 #ifndef BASE_LAZY_INSTANCE_H_
 #define BASE_LAZY_INSTANCE_H_
 #pragma once
 
+#include <new>  // For placement new.
+
 #include "base/atomicops.h"
 #include "base/basictypes.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
+#include "base/thread_restrictions.h"
 
 namespace base {
 
 template <typename Type>
 struct DefaultLazyInstanceTraits {
+  static const bool kAllowedToAccessOnNonjoinableThread = false;
+
   static Type* New(void* instance) {
     // 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(void* instance) {
     // Explicitly call the destructor.
     reinterpret_cast<Type*>(instance)->~Type();
   }
 };
 
 template <typename Type>
 struct LeakyLazyInstanceTraits {
+  static const bool kAllowedToAccessOnNonjoinableThread = true;
+
   static Type* New(void* instance) {
     return DefaultLazyInstanceTraits<Type>::New(instance);
   }
   // Rather than define an empty Delete function, we make Delete itself
   // a null pointer.  This allows us to completely sidestep registering
   // this object with an AtExitManager, which allows you to use
   // LeakyLazyInstanceTraits in contexts where you don't have an
   // AtExitManager.
   static void (*Delete)(void* instance);
 };
@@ skipping 35 matching lines @@
  public:
   explicit LazyInstance(LinkerInitialized x) : LazyInstanceHelper(x) { }
   // Declaring a destructor (even if it's empty) will cause MSVC to register a
   // static initializer to register the empty destructor with atexit().
 
   Type& Get() {
     return *Pointer();
   }
 
   Type* Pointer() {
+    if (!Traits::kAllowedToAccessOnNonjoinableThread)
+      base::ThreadRestrictions::AssertSingletonAllowed();
+
     // We will hopefully have fast access when the instance is already created.
     if ((base::subtle::NoBarrier_Load(&state_) != STATE_CREATED) &&
         NeedsInstance()) {
       // Create the instance in the space provided by |buf_|.
       instance_ = Traits::New(buf_);
       CompleteInstance(instance_, Traits::Delete);
     }
 
     // This annotation helps race detectors recognize correct lock-less
     // synchronization between different threads calling Pointer().
     // We suggest dynamic race detection tool that "Traits::New" above
     // and CompleteInstance(...) happens before "return instance_" below.
     // See the corresponding HAPPENS_BEFORE in CompleteInstance(...).
     ANNOTATE_HAPPENS_AFTER(&state_);
-
     return instance_;
   }
 
  private:
   int8 buf_[sizeof(Type)];  // Preallocate the space for the Type instance.
   Type *instance_;
 
   DISALLOW_COPY_AND_ASSIGN(LazyInstance);
 };
 
 }  // namespace base
 
 #endif  // BASE_LAZY_INSTANCE_H_