Set HistogramEnumerationFunction even when Partitions are initialized

Source/wtf/Partitions.h

Index: Source/wtf/Partitions.h
diff --git a/Source/wtf/Partitions.h b/Source/wtf/Partitions.h
index 858a693e010766d578a06a8cb93c8e87e5624cba..4e85794ec02e46bf1eca3ac6bfa10b6615e29ed3 100644
--- a/Source/wtf/Partitions.h
+++ b/Source/wtf/Partitions.h
@@ -39,7 +39,11 @@ namespace WTF {
 
 class WTF_EXPORT Partitions {
 public:
-    static void initialize(HistogramEnumerationFunction = nullptr);
+    static void initialize();
+    // TODO(bashi): Remove this function and make initialize() take
+    // HistogramEnumerationFunction when we can make sure that WTF::initialize()
+    // is called before using this class.
+    static void setHistogramEnumeration(HistogramEnumerationFunction);
     static void shutdown();
     ALWAYS_INLINE static PartitionRootGeneric* bufferPartition()
     {