Track JS allocations as they arrive with no affection on performance when tracking is switched off

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index e81a0e3b3b3e3dd7fc7ec8826f323949e6f093d3..4722aec23815476a3a8c6b7e65adb68865a31c50 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -2100,7 +2100,8 @@ class ScavengingVisitor : public StaticVisitorBase {
     if (logging_and_profiling_mode == LOGGING_AND_PROFILING_ENABLED) {
       // Update NewSpace stats if necessary.
       RecordCopiedObject(heap, target);
-      HEAP_PROFILE(heap, ObjectMoveEvent(source->address(), target->address()));
+      HEAP_PROFILE(heap,
+                   ObjectMoveEvent(source->address(), target->address(), size));
       Isolate* isolate = heap->isolate();
       if (isolate->logger()->is_logging_code_events() ||
           isolate->cpu_profiler()->is_profiling()) {
@@ -4975,6 +4976,13 @@ MaybeObject* Heap::CopyJSObject(JSObject* source, AllocationSite* site) {
       alloc_memento->set_map_no_write_barrier(allocation_memento_map());
       ASSERT(site->map() == allocation_site_map());
       alloc_memento->set_allocation_site(site, SKIP_WRITE_BARRIER);
+      HeapProfiler* profiler = isolate()->heap_profiler();

[Hannes Payer (out of office), 2013/10/02 18:00:29]

Why do you track the allocation of the memento separately? And why don't you
account the allocation in the if branch before? 

[Hannes Payer (out of office), 2013/10/02 18:20:04]

Ok, ignore question two, because you allocate using AllocateRaw. But why do you
track the memento separately?

[Alexandra Mikhaylova, 2013/10/03 16:27:55]

The memento is treated as a separate HeapObject when the heap is being iterated,
so if we don't track it, we'll have untracked allocations.

[Hannes Payer (out of office), 2013/10/10 18:54:40]

OK. You could also ignore the mementos since they are VM specific and never
visible to the user. Mementos allocated in optimized code are allocated together
with their parent object, so you cannot track them. They are manually folded
into the parent object.

+      if (profiler->is_tracking_allocations()) {
+        profiler->UpdateObjectSizeEvent(HeapObject::cast(clone)->address(),
+                                        object_size);
+        profiler->NewObjectEvent(alloc_memento->address(),
+                                 AllocationMemento::kSize);
+      }
     }
   }