Reland of SkOncePtr -> SkOnce

src/core/SkMessageBus.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkMessageBus_DEFINED
 #define SkMessageBus_DEFINED
 
 #include "SkMutex.h"
-#include "SkOncePtr.h"
+#include "SkOnce.h"
 #include "SkTArray.h"
 #include "SkTDArray.h"
 #include "SkTypes.h"
 
 template <typename Message>
 class SkMessageBus : SkNoncopyable {
 public:
     // Post a message to be received by all Inboxes for this Message type.  Threadsafe.
     static void Post(const Message& m);
 
@@ skipping 17 matching lines @@
     SkMessageBus();
     static SkMessageBus* Get();
 
     SkTDArray<Inbox*> fInboxes;
     SkMutex           fInboxesMutex;
 };
 
 // This must go in a single .cpp file, not some .h, or we risk creating more than one global
 // SkMessageBus per type when using shared libraries.  NOTE: at most one per file will compile.
 #define DECLARE_SKMESSAGEBUS_MESSAGE(Message)                      \
-    SK_DECLARE_STATIC_ONCE_PTR(SkMessageBus<Message>, bus);        \
     template <>                                                    \
     SkMessageBus<Message>* SkMessageBus<Message>::Get() {          \
-        return bus.get([]{ return new SkMessageBus<Message>(); }); \
+        static SkOnce once;                                        \
+        static SkMessageBus<Message>* bus;                         \
+        once([] { bus = new SkMessageBus<Message>(); });           \
+        return bus;                                                \
     }
 
 //   ----------------------- Implementation of SkMessageBus::Inbox -----------------------
 
 template<typename Message>
 SkMessageBus<Message>::Inbox::Inbox() {
     // Register ourselves with the corresponding message bus.
     SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
     SkAutoMutexAcquire lock(bus->fInboxesMutex);
     bus->fInboxes.push(this);
@@ skipping 35 matching lines @@
 template <typename Message>
 /*static*/ void SkMessageBus<Message>::Post(const Message& m) {
     SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
     SkAutoMutexAcquire lock(bus->fInboxesMutex);
     for (int i = 0; i < bus->fInboxes.count(); i++) {
         bus->fInboxes[i]->receive(m);
     }
 }
 
 #endif  // SkMessageBus_DEFINED