Attempt no. 3 to fix Heap::IsHeapIterable and HeapIterator

src/heap-snapshot-generator.cc

Index: src/heap-snapshot-generator.cc
diff --git a/src/heap-snapshot-generator.cc b/src/heap-snapshot-generator.cc
index cafee77b4ce10d20be74ee3df7fe290349cff63f..ef752ff20d96fe3aa611fcbfbd54e6130feed54d 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -2569,10 +2569,6 @@ bool HeapSnapshotGenerator::GenerateSnapshot() {
   CHECK(!debug_heap->map_space()->was_swept_conservatively());
 #endif
 
-  // The following code uses heap iterators, so we want the heap to be
-  // stable. It should follow TagGlobalObjects as that can allocate.
-  DisallowHeapAllocation no_alloc;
-
 #ifdef VERIFY_HEAP
   debug_heap->Verify();
 #endif