Add a UseCounter that measures the amount of memory used in PartitionAlloc

Source/wtf/WTF.h

Index: Source/wtf/WTF.h
diff --git a/Source/wtf/WTF.h b/Source/wtf/WTF.h
index c172996d415643ed56617df7aae8834437cc70e5..1f14c68abcc983c9fbe60871bf5a47ea341b8d53 100644
--- a/Source/wtf/WTF.h
+++ b/Source/wtf/WTF.h
@@ -37,8 +37,10 @@
 
 namespace WTF {
 
+typedef void(*HistogramEnumerationFunction)(const char* name, int sample, int boundaryValue);
+
 // This function must be called exactly once from the main thread before using anything else in WTF.
-WTF_EXPORT void initialize(TimeFunction currentTimeFunction, TimeFunction monotonicallyIncreasingTimeFunction);
+WTF_EXPORT void initialize(TimeFunction currentTimeFunction, TimeFunction monotonicallyIncreasingTimeFunction, HistogramEnumerationFunction);
 WTF_EXPORT void shutdown();
 WTF_EXPORT bool isShutdown();