Add experimental support for tracing the state of the VM heap to a file

src/incremental-marking.cc

 // Copyright 2011 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 668 matching lines @@
 
   intptr_t bytes_to_process = allocated_ * allocation_marking_factor_;
 
   double start = 0;
 
   if (FLAG_trace_incremental_marking || FLAG_trace_gc) {
     start = OS::TimeCurrentMillis();
   }
 
   if (state_ == SWEEPING) {
+    heap_->VisualizerTimeStamp(HeapVisualizer::kSweeping);
     if (heap_->old_pointer_space()->AdvanceSweeper(bytes_to_process) &&
         heap_->old_data_space()->AdvanceSweeper(bytes_to_process)) {
       StartMarking();
     }
   } else if (state_ == MARKING) {
+    heap_->VisualizerTimeStamp(HeapVisualizer::kMarking);
     Map* filler_map = heap_->one_pointer_filler_map();
     Map* global_context_map = heap_->global_context_map();
     IncrementalMarkingMarkingVisitor marking_visitor(heap_, this);
     while (!marking_deque_.IsEmpty() && bytes_to_process > 0) {
       HeapObject* obj = marking_deque_.Pop();
 
       // Explicitly skip one word fillers. Incremental markbit patterns are
       // correct only for objects that occupy at least two words.
       Map* map = obj->map();
       if (map == filler_map) continue;
@@ skipping 67 matching lines @@
     }
   }
 
   if (FLAG_trace_incremental_marking || FLAG_trace_gc) {
     double end = OS::TimeCurrentMillis();
     double delta = (end - start);
     longest_step_ = Max(longest_step_, delta);
     steps_took_ += delta;
     steps_took_since_last_gc_ += delta;
   }
+  heap_->VisualizerTimeStamp(HeapVisualizer::kRunning);
 }
 
 
 void IncrementalMarking::ResetStepCounters() {
   steps_count_ = 0;
   steps_took_ = 0;
   longest_step_ = 0.0;
   old_generation_space_available_at_start_of_incremental_ =
       SpaceLeftInOldSpace();
   old_generation_space_used_at_start_of_incremental_ =
       heap_->PromotedTotalSize();
   steps_count_since_last_gc_ = 0;
   steps_took_since_last_gc_ = 0;
   bytes_rescanned_ = 0;
   allocation_marking_factor_ = kInitialAllocationMarkingFactor;
 }
 
 
 int64_t IncrementalMarking::SpaceLeftInOldSpace() {
   return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSize();
 }
 
 } }  // namespace v8::internal