[vm, gc] Require a safepoint for heap iteration.

runtime/vm/compiler_stats.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/compiler_stats.h"
 
 #include "vm/flags.h"
 #include "vm/log.h"
 #include "vm/object_graph.h"
 #include "vm/object_store.h"
@@ skipping 105 matching lines @@
   va_list args;
   va_start(args, format);
   stats->text = zone->VPrint(format, args);
   va_end(args);
 }
 
 void CompilerStats::Update() {
   // Traverse the heap and compute number of tokens in all
   // TokenStream objects.
   num_tokens_total = 0;
-  TokenStreamVisitor visitor(this);
-  isolate_->heap()->IterateObjects(&visitor);
-  Dart::vm_isolate()->heap()->IterateObjects(&visitor);
+
+  {
+    HeapIterationScope iteration(Thread::Current());
+    TokenStreamVisitor visitor(this);
+    iteration.IterateObjects(&visitor);
+    iteration.IterateVMIsolateObjects(&visitor);
+  }
 }
 
 void CompilerStats::EnableBenchmark() {
   FLAG_compiler_stats = true;
   use_benchmark_output = true;
 }
 
 // Generate output for Golem benchmark harness. If the output format
 // changes, the parsing function in Golem must be updated.
 char* CompilerStats::BenchmarkOutput() {
@@ skipping 156 matching lines @@
   log.Print("  VarDesc size:          %" Pd64 " KB\n", vardesc_size / 1024);
   log.Flush();
   char* stats_text = text;
   text = NULL;
   return stats_text;
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart