[heap] Remove unused GC idle time histograms.

This patch removes tracking of
- V8.GCIdleTimeAllottedInMS
- V8.GCIdleTimeLimit.Overshot
- V8.GCIdleTimeLimit.Undershot

BUG=chromium:751045

Change-Id: Iccaa0fff609d3caa4cf38ebcc8aca7cdca33c442
Reviewed-on: https://chromium-review.googlesource.com/595588
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47144}

src/counters.h

@@ -994,10 +994,6 @@ class RuntimeCallTimerScope {
 #define HISTOGRAM_RANGE_LIST(HR)                                              \
   /* Generic range histograms */                                              \
   HR(detached_context_age_in_gc, V8.DetachedContextAgeInGC, 0, 20, 21)        \
-  HR(gc_idle_time_allotted_in_ms, V8.GCIdleTimeAllottedInMS, 0, 10000, 101)   \
-  HR(gc_idle_time_limit_overshot, V8.GCIdleTimeLimit.Overshot, 0, 10000, 101) \
-  HR(gc_idle_time_limit_undershot, V8.GCIdleTimeLimit.Undershot, 0, 10000,    \
-     101)                                                                     \
   HR(code_cache_reject_reason, V8.CodeCacheRejectReason, 1, 6, 6)             \
   HR(errors_thrown_per_context, V8.ErrorsThrownPerContext, 0, 200, 20)        \
   HR(debug_feature_usage, V8.DebugFeatureUsage, 1, 7, 7)                      \

src/heap/heap.cc

@@ -4731,9 +4731,6 @@ void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
 
   contexts_disposed_ = 0;
 
-  isolate()->counters()->gc_idle_time_allotted_in_ms()->AddSample(
-      static_cast<int>(idle_time_in_ms));
-
   if (deadline_in_ms - start_ms >
       GCIdleTimeHandler::kMaxFrameRenderingIdleTime) {
     int committed_memory = static_cast<int>(CommittedMemory() / KB);
@@ -4744,16 +4741,6 @@ void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
         start_ms, used_memory);
   }
 
-  if (deadline_difference >= 0) {
-    if (action.type != DONE && action.type != DO_NOTHING) {
-      isolate()->counters()->gc_idle_time_limit_undershot()->AddSample(
-          static_cast<int>(deadline_difference));
-    }
-  } else {
-    isolate()->counters()->gc_idle_time_limit_overshot()->AddSample(
-        static_cast<int>(-deadline_difference));
-  }
-
   if ((FLAG_trace_idle_notification && action.type > DO_NOTHING) ||
       FLAG_trace_idle_notification_verbose) {
     isolate_->PrintWithTimestamp(