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

src/spaces-inl.h

Index: src/spaces-inl.h
===================================================================
--- src/spaces-inl.h	(revision 9457)
+++ src/spaces-inl.h	(working copy)
@@ -170,6 +170,16 @@
   owner->Free(page->ObjectAreaStart(),
               static_cast<int>(page->ObjectAreaEnd() -
                                page->ObjectAreaStart()));
+  for (HeapVisualizer* vis = heap->visualizer();
+       vis != NULL;
+       vis = vis->next()) {
+    vis->Name(v8::HeapVisualizer::kHeapOverheadPseudoSpaceIdentity,
+              reinterpret_cast<uintptr_t>(page->address()),
+              page->ObjectAreaStart() - page->address());
+    vis->ConstantAllocation(reinterpret_cast<uintptr_t>(page->address()),
+                            page->ObjectAreaStart() - page->address(),
+                            0);
+  }
 
   heap->incremental_marking()->SetOldSpacePageFlags(chunk);
 
@@ -184,6 +194,17 @@
 }
 
 
+void PagedSpace::SetTop(Address top, Address limit) {
+  if (heap()->has_visualizer()) {
+    VisualizeTopChange(top);
+  }
+  ASSERT(top == limit ||
+         Page::FromAddress(top) == Page::FromAddress(limit - 1));
+  allocation_info_.top = top;
+  allocation_info_.limit = limit;
+}
+
+
 void MemoryChunk::set_scan_on_scavenge(bool scan) {
   if (scan) {
     if (!scan_on_scavenge()) heap_->increment_scan_on_scavenge_pages();