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

runtime/vm/runtime_entry.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/runtime_entry.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 78 matching lines @@
             gc_at_instance_allocation,
             NULL,
             "Perform a GC before allocation of instances of "
             "the specified class");
 #endif
 
 #if defined(TESTING) || defined(DEBUG)
 void VerifyOnTransition() {
   Thread* thread = Thread::Current();
   TransitionGeneratedToVM transition(thread);
-  thread->isolate()->heap()->WaitForSweeperTasks(thread);
-  SafepointOperationScope safepoint_scope(thread);
   VerifyPointersVisitor::VerifyPointers();
   thread->isolate()->heap()->Verify();
 }
 #endif
 
 // Add function to a class and that class to the class dictionary so that
 // frame walking can be used.
 const Function& RegisterFakeFunction(const char* name, const Code& code) {
   Thread* thread = Thread::Current();
   const String& class_name = String::Handle(Symbols::New(thread, "ownerClass"));
@@ skipping 2252 matching lines @@
     true /* is_float */,
     reinterpret_cast<RuntimeFunction>(static_cast<UnaryMathCFunction>(&tan)));
 
 DEFINE_RAW_LEAF_RUNTIME_ENTRY(
     LibcAtan,
     1,
     true /* is_float */,
     reinterpret_cast<RuntimeFunction>(static_cast<UnaryMathCFunction>(&atan)));
 
 }  // namespace dart