Add parallel recompilation time to histogram and plot execution pause times.

src/heap.cc

 // 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:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 626 matching lines @@
 
   { GCTracer tracer(this, gc_reason, collector_reason);
     GarbageCollectionPrologue();
     // The GC count was incremented in the prologue.  Tell the tracer about
     // it.
     tracer.set_gc_count(gc_count_);
 
     // Tell the tracer which collector we've selected.
     tracer.set_collector(collector);
 
-    HistogramTimer* rate = (collector == SCAVENGER)
-        ? isolate_->counters()->gc_scavenger()
-        : isolate_->counters()->gc_compactor();
-    rate->Start();
-    next_gc_likely_to_collect_more =
-        PerformGarbageCollection(collector, &tracer);
-    rate->Stop();
+    {
+      HistogramTimerScope histogram_timer_scope(
+          (collector == SCAVENGER) ? isolate_->counters()->gc_scavenger()
+                                   : isolate_->counters()->gc_compactor());
+      next_gc_likely_to_collect_more =
+          PerformGarbageCollection(collector, &tracer);
+    }
 
     ASSERT(collector == SCAVENGER || incremental_marking()->IsStopped());
 
     // This can do debug callbacks and restart incremental marking.
     GarbageCollectionEpilogue();
   }
 
   if (incremental_marking()->IsStopped()) {
     if (incremental_marking()->WorthActivating() && NextGCIsLikelyToBeFull()) {
       incremental_marking()->Start();
@@ skipping 6841 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal