Revert of SK_DECLARE_STATIC_MUTEX -> static SkMutex

src/lazy/SkDiscardableMemoryPool.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDiscardableMemory.h"
 #include "SkDiscardableMemoryPool.h"
 #include "SkImageGenerator.h"
@@ skipping 226 matching lines @@
     SkAutoMutexAcquire autoMutexAcquire(fMutex);
     this->dumpDownTo(0);
 }
 
 }  // namespace
 
 SkDiscardableMemoryPool* SkDiscardableMemoryPool::Create(size_t size, SkMutex* mutex) {
     return new DiscardableMemoryPool(size, mutex);
 }
 
-static SkMutex gMutex;
+SK_DECLARE_STATIC_MUTEX(gMutex);
 
 SkDiscardableMemoryPool* SkGetGlobalDiscardableMemoryPool() {
     static SkOnce once;
     static SkDiscardableMemoryPool* global;
     once([]{
         global = SkDiscardableMemoryPool::Create(SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE,
                                                  &gMutex);
     });
     return global;
 }