Don't use TLS for space iterators.

src/heap-profiler.h

Index: src/heap-profiler.h
diff --git a/src/heap-profiler.h b/src/heap-profiler.h
index 9d3ba6f1112dc99b3366e799bb0a3bd9dd984535..c8c94f58d60f485c646b57e08fa70f7741790541 100644
--- a/src/heap-profiler.h
+++ b/src/heap-profiler.h
@@ -83,7 +83,7 @@ class HeapProfiler {
   }
 
  private:
-  HeapProfiler();
+  explicit HeapProfiler(Heap* heap);
   ~HeapProfiler();
   HeapSnapshot* TakeSnapshotImpl(
       const char* name,
@@ -101,6 +101,8 @@ class HeapProfiler {
   void StopHeapObjectsTrackingImpl();
   SnapshotObjectId PushHeapObjectsStatsImpl(OutputStream* stream);
 
+  Heap* heap() const { return snapshots_->heap(); }
+
   HeapSnapshotsCollection* snapshots_;
   unsigned next_snapshot_uid_;
   List<v8::HeapProfiler::WrapperInfoCallback> wrapper_callbacks_;