Make members of Singleton<T> private and only visible to the singleton type.

net/disk_cache/file_win.cc

 // Copyright (c) 2006-2010 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.
 
 #include "net/disk_cache/file.h"
 
 #include "base/file_path.h"
+#include "base/lazy_instance.h"
 #include "base/message_loop.h"
-#include "base/singleton.h"
 #include "net/disk_cache/disk_cache.h"
 
 namespace {
 
 // Structure used for asynchronous operations.
 struct MyOverlapped {
   MyOverlapped(disk_cache::File* file, size_t offset,
                disk_cache::FileIOCallback* callback);
   ~MyOverlapped() {}
   OVERLAPPED* overlapped() {
     return &context_.overlapped;
   }
 
   MessageLoopForIO::IOContext context_;
   scoped_refptr<disk_cache::File> file_;
   disk_cache::FileIOCallback* callback_;
 };
 
 COMPILE_ASSERT(!offsetof(MyOverlapped, context_), starts_with_overlapped);
 
 // Helper class to handle the IO completion notifications from the message loop.
 class CompletionHandler : public MessageLoopForIO::IOHandler {
   virtual void OnIOCompleted(MessageLoopForIO::IOContext* context,
                              DWORD actual_bytes, DWORD error);
 };
 
+static base::LazyInstance<CompletionHandler> g_completion_handler(
+    base::LINKER_INITIALIZED);
+
 void CompletionHandler::OnIOCompleted(MessageLoopForIO::IOContext* context,
                                       DWORD actual_bytes, DWORD error) {
   MyOverlapped* data = reinterpret_cast<MyOverlapped*>(context);
 
   if (error) {
     DCHECK(!actual_bytes);
     actual_bytes = static_cast<DWORD>(-1);
     NOTREACHED();
   }
 
   if (data->callback_)
     data->callback_->OnFileIOComplete(static_cast<int>(actual_bytes));
 
   delete data;
 }
 
 MyOverlapped::MyOverlapped(disk_cache::File* file, size_t offset,
                            disk_cache::FileIOCallback* callback) {
   memset(this, 0, sizeof(*this));
-  context_.handler = Singleton<CompletionHandler>::get();
+  context_.handler = g_completion_handler.Pointer();
   context_.overlapped.Offset = static_cast<DWORD>(offset);
   file_ = file;
   callback_ = callback;
 }
 
 }  // namespace
 
 namespace disk_cache {
 
 File::File(base::PlatformFile file)
     : init_(true), mixed_(true), platform_file_(INVALID_HANDLE_VALUE),
       sync_platform_file_(file) {
 }
 
 bool File::Init(const FilePath& name) {
   DCHECK(!init_);
   if (init_)
     return false;
 
   DWORD sharing = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
   DWORD access = GENERIC_READ | GENERIC_WRITE | DELETE;
   platform_file_ = CreateFile(name.value().c_str(), access, sharing, NULL,
                               OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
 
   if (INVALID_HANDLE_VALUE == platform_file_)
     return false;
 
   MessageLoopForIO::current()->RegisterIOHandler(
-      platform_file_, Singleton<CompletionHandler>::get());
+      platform_file_, g_completion_handler.Pointer());
 
   init_ = true;
   sync_platform_file_  = CreateFile(name.value().c_str(), access, sharing, NULL,
                                     OPEN_EXISTING, 0, NULL);
 
   if (INVALID_HANDLE_VALUE == sync_platform_file_)
     return false;
 
   return true;
 }
@@ skipping 153 matching lines @@
     return ULONG_MAX;
 
   return static_cast<size_t>(size.LowPart);
 }
 
 // Static.
 void File::WaitForPendingIO(int* num_pending_io) {
   while (*num_pending_io) {
     // Asynchronous IO operations may be in flight and the completion may end
     // up calling us back so let's wait for them.
-    MessageLoopForIO::IOHandler* handler = Singleton<CompletionHandler>::get();
+    MessageLoopForIO::IOHandler* handler = g_completion_handler.Pointer();
     MessageLoopForIO::current()->WaitForIOCompletion(100, handler);
   }
 }
 
 }  // namespace disk_cache