Wait for sweeper threads only if we have to.

src/heap-snapshot-generator.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/heap-snapshot-generator-inl.h"
 
 #include "src/allocation-tracker.h"
 #include "src/code-stubs.h"
@@ skipping 2568 matching lines @@
   // As a temporary solution we call GC twice.
   heap_->CollectAllGarbage(
       Heap::kMakeHeapIterableMask,
       "HeapSnapshotGenerator::GenerateSnapshot");
   heap_->CollectAllGarbage(
       Heap::kMakeHeapIterableMask,
       "HeapSnapshotGenerator::GenerateSnapshot");
 
 #ifdef VERIFY_HEAP
   Heap* debug_heap = heap_;
-  CHECK(!debug_heap->old_data_space()->was_swept_conservatively());
-  CHECK(!debug_heap->old_pointer_space()->was_swept_conservatively());
-  CHECK(!debug_heap->code_space()->was_swept_conservatively());
-  CHECK(!debug_heap->cell_space()->was_swept_conservatively());
-  CHECK(!debug_heap->property_cell_space()->
-        was_swept_conservatively());
-  CHECK(!debug_heap->map_space()->was_swept_conservatively());
+  CHECK(debug_heap->old_data_space()->is_iterable());
+  CHECK(debug_heap->old_pointer_space()->is_iterable());
+  CHECK(debug_heap->code_space()->is_iterable());
+  CHECK(debug_heap->cell_space()->is_iterable());
+  CHECK(debug_heap->property_cell_space()->is_iterable());
+  CHECK(debug_heap->map_space()->is_iterable());
 #endif
 
 #ifdef VERIFY_HEAP
   debug_heap->Verify();
 #endif
 
   SetProgressTotal(2);  // 2 passes.
 
 #ifdef VERIFY_HEAP
   debug_heap->Verify();
@@ skipping 565 matching lines @@
   writer_->AddString("\"<dummy>\"");
   for (int i = 1; i < sorted_strings.length(); ++i) {
     writer_->AddCharacter(',');
     SerializeString(sorted_strings[i]);
     if (writer_->aborted()) return;
   }
 }
 
 
 } }  // namespace v8::internal