[heap] Add store and slots buffer clearing timers to --trace-gc-nvp.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 279 matching lines @@
     heap()->code_space()->EvictEvacuationCandidatesFromLinearAllocationArea();
 
     compacting_ = evacuation_candidates_.length() > 0;
   }
 
   return compacting_;
 }
 
 
 void MarkCompactCollector::ClearInvalidStoreAndSlotsBufferEntries() {
-  heap_->store_buffer()->ClearInvalidStoreBufferEntries();
+  {
+    GCTracer::Scope gc_scope(heap()->tracer(),
+                             GCTracer::Scope::MC_STORE_BUFFER_CLEAR);
+    heap_->store_buffer()->ClearInvalidStoreBufferEntries();
+  }
 
-  int number_of_pages = evacuation_candidates_.length();
-  for (int i = 0; i < number_of_pages; i++) {
-    Page* p = evacuation_candidates_[i];
-    SlotsBuffer::RemoveInvalidSlots(heap_, p->slots_buffer());
+  {
+    GCTracer::Scope gc_scope(heap()->tracer(),
+                             GCTracer::Scope::MC_SLOTS_BUFFER_CLEAR);
+    int number_of_pages = evacuation_candidates_.length();
+    for (int i = 0; i < number_of_pages; i++) {
+      Page* p = evacuation_candidates_[i];
+      SlotsBuffer::RemoveInvalidSlots(heap_, p->slots_buffer());
+    }
   }
 }
 
 
 #ifdef VERIFY_HEAP
 static void VerifyValidSlotsBufferEntries(Heap* heap, PagedSpace* space) {
   PageIterator it(space);
   while (it.has_next()) {
     Page* p = it.next();
     SlotsBuffer::VerifySlots(heap, p->slots_buffer());
@@ skipping 4296 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(&rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8