SkOnce: add option to call another cleanup function once at exit.

src/core/SkData.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkData.h"
 #include "SkFlattenableBuffers.h"
 #include "SkOSFile.h"
@@ skipping 30 matching lines @@
         length = available;
     }
     SkASSERT(length > 0);
 
     memcpy(buffer, this->bytes() + offset, length);
     return length;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void SkData::NewEmptyImpl(SkData** empty) {
-    *empty = new SkData(NULL, 0, NULL, NULL);
+static SkData* gEmptyDataRef = NULL;
+static void cleanup_gEmptyDataRef() { gEmptyDataRef->unref(); }
+
+void SkData::NewEmptyImpl(int) {
+    gEmptyDataRef = new SkData(NULL, 0, NULL, NULL);
 }
 
 SkData* SkData::NewEmpty() {
-    static SkData* gEmptyRef;
     SK_DECLARE_STATIC_ONCE(once);
-    SkOnce(&once, SkData::NewEmptyImpl, &gEmptyRef);
-    gEmptyRef->ref();
-    return gEmptyRef;
+    SkOnce(&once, SkData::NewEmptyImpl, 0, cleanup_gEmptyDataRef);
+    gEmptyDataRef->ref();
+    return gEmptyDataRef;
 }
 
 // assumes fPtr was allocated via sk_malloc
 static void sk_free_releaseproc(const void* ptr, size_t, void*) {
     sk_free((void*)ptr);
 }
 
 SkData* SkData::NewFromMalloc(const void* data, size_t length) {
     return new SkData(data, length, sk_free_releaseproc, NULL);
 }
@@ skipping 79 matching lines @@
 SkData* SkData::NewWithCString(const char cstr[]) {
     size_t size;
     if (NULL == cstr) {
         cstr = "";
         size = 1;
     } else {
         size = strlen(cstr) + 1;
     }
     return NewWithCopy(cstr, size);
 }