Add a histogram timer around low memory notifications from API

BUG=397026
R=hpayer@chromium.org, ernstm@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/416853002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22604 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/api.cc

@@ -5063,7 +5063,11 @@ bool v8::V8::IdleNotification(int hint) {
 void v8::V8::LowMemoryNotification() {
   i::Isolate* isolate = i::Isolate::Current();
   if (isolate == NULL || !isolate->IsInitialized()) return;
-  isolate->heap()->CollectAllAvailableGarbage("low memory notification");
+  {
+    i::HistogramTimerScope idle_notification_scope(
+        isolate->counters()->gc_low_memory_notification());
+    isolate->heap()->CollectAllAvailableGarbage("low memory notification");
+  }
 }
 
 
@@ -6723,7 +6727,11 @@ bool v8::Isolate::IdleNotification(int idle_time_in_ms) {
 
 void v8::Isolate::LowMemoryNotification() {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
-  isolate->heap()->CollectAllAvailableGarbage("low memory notification");
+  {
+    i::HistogramTimerScope idle_notification_scope(
+        isolate->counters()->gc_low_memory_notification());
+    isolate->heap()->CollectAllAvailableGarbage("low memory notification");
+  }
 }
 
 

src/counters.h

@@ -299,6 +299,7 @@ class HistogramTimerScope BASE_EMBEDDED {
   HT(gc_context, V8.GCContext) /* GC context cleanup time */ \
   HT(gc_idle_notification, V8.GCIdleNotification)            \
   HT(gc_incremental_marking, V8.GCIncrementalMarking)        \
+  HT(gc_low_memory_notification, V8.GCLowMemoryNotification) \
   /* Parsing timers. */                                      \
   HT(parse, V8.Parse)                                        \
   HT(parse_lazy, V8.ParseLazy)                               \