Added histogram to track distribution of requested idle notifications.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index e75c7231ffdd9ea90349584f3a21336e50db9506..bee5f1ccc4f5bd84b78732bc3c18cfd1b2723694 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -2277,6 +2277,11 @@ class Heap {
   // deoptimization triggered by garbage collection.
   int gcs_since_last_deopt_;
 
+  static const int kMaxIdleNotificationHistogramSample = 1000;
+
+  // A histogram that displays the distribution of idle notification calls.
+  void* idle_notification_histogram_;

[rmcilroy, 2014/07/25 09:38:29]

I'd probably call this idle_notification_hint_histogram_ (or maybe something
like idle_gc_allotted_time_histogram_ for the new scheduler based time).

Also, any reason this isn't in counters.h - there is already a
gc_idle_notification in HISTOGRAM_TIMER_LIST.

[Hannes Payer (out of office), 2014/07/25 10:08:20]

Yeah, we do not really have a category for this counter. I could create a "fake"
HistogramTimer. The only similar histogram I found was the script_histogram_.
WDYT?

+
 #ifdef VERIFY_HEAP
   int no_weak_object_verification_scope_depth_;
 #endif