Fix thread unsafe mutex initialization.

include/core/SkInstCnt.h

Index: include/core/SkInstCnt.h
diff --git a/include/core/SkInstCnt.h b/include/core/SkInstCnt.h
index 1839ee1dbdc6720d9c6b0870ea10e52dbe901c7a..e4b43d130b94b6a2ab9303c3c6c1170f7c3722ff 100644
--- a/include/core/SkInstCnt.h
+++ b/include/core/SkInstCnt.h
@@ -73,9 +73,14 @@ extern bool gPrintInstCount;
             return gChildren;                                               \
         }                                                                   \
                                                                             \
+        static void create_mutex(SkMutex** mutex) {                         \
+            *mutex = SkNEW(SkMutex);                                        \
+        }                                                                   \
         static SkBaseMutex& GetChildrenMutex() {                            \
-            SK_DECLARE_STATIC_MUTEX(childrenMutex);                         \
-            return childrenMutex;                                           \
+            static SkMutex* childrenMutex;                                  \
+            SK_DECLARE_STATIC_ONCE(once);                                   \
+            SkOnce(&once, className::SkInstanceCountHelper::create_mutex, &childrenMutex);\
+            return *childrenMutex;                                          \

[bungeman-skia, 2014/07/25 15:44:07]

Making this body look like

SK_DECLARE_STATIC_LAZY_PTR(SkMutex, childrenMutex);
return *childrenMutex.get();

seems like it would work even better, but this file is in include/core and
SkLazyPtr.h is in src/core, which might not be on the search path. I think that
would make the include something like #include "../../src/core/SkLazyPtr.h"
which requires that 'src' and 'include' be next to each other.

         }                                                                   \
                                                                             \
     } fInstanceCountHelper;                                                 \