Factor out a Histogram class from HistogramTimer, and use it to measure external fragmentation

src/v8-counters.cc

Index: src/v8-counters.cc
diff --git a/src/v8-counters.cc b/src/v8-counters.cc
index c6aa9cb7f8a3ed8bce78dd03628f9af25c353c70..04fd0775761f31ccf4f076b4f48249b37c886c1a 100644
--- a/src/v8-counters.cc
+++ b/src/v8-counters.cc
@@ -1,4 +1,4 @@
-// Copyright 2007-2008 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -34,11 +34,17 @@ namespace internal {
 
 Counters::Counters() {
 #define HT(name, caption) \
-    HistogramTimer name = { #caption, NULL, false, 0, 0 }; \
+    HistogramTimer name = { {#caption, 0, 10000, 50, NULL, false}, 0, 0 }; \
     name##_ = name;
     HISTOGRAM_TIMER_LIST(HT)
 #undef HT
 
+#define HP(name, caption) \
+    Histogram name = { #caption, 0, 101, 100, NULL, false }; \
+    name##_ = name;
+    HISTOGRAM_PERCENTAGE_LIST(HP)
+#undef HP
+
 #define SC(name, caption) \
     StatsCounter name = { "c:" #caption, NULL, false };\
     name##_ = name;