Moves the top_ and end_ words of the Scavenger into mutator thread.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 8ca2e728aab1eee98f6e5ec088f6a035d8da8391..932cc9a7d7ed908e8d3270aaa640c618b11c0681 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -2658,6 +2658,7 @@ Thread* Isolate::ScheduleThread(bool is_mutator, bool bypass_safepoint) {
     thread->isolate_ = this;
     ASSERT(heap() != NULL);
     thread->heap_ = heap();
+
     thread->set_os_thread(os_thread);
     ASSERT(thread->execution_state() == Thread::kThreadInNative);
     thread->set_execution_state(Thread::kThreadInVM);
@@ -2667,6 +2668,10 @@ Thread* Isolate::ScheduleThread(bool is_mutator, bool bypass_safepoint) {
     os_thread->set_thread(thread);
     if (is_mutator) {
       mutator_thread_ = thread;
+      if (this != Dart::vm_isolate()) {
+        mutator_thread_->set_top(heap()->new_space()->top());
+        mutator_thread_->set_end(heap()->new_space()->end());
+      }
     }
     Thread::SetCurrent(thread);
     os_thread->EnableThreadInterrupts();
@@ -2706,6 +2711,12 @@ void Isolate::UnscheduleThread(Thread* thread,
   os_thread->set_thread(NULL);
   OSThread::SetCurrent(os_thread);
   if (is_mutator) {
+    if (this != Dart::vm_isolate()) {
+      heap()->new_space()->set_top(mutator_thread_->top_);
+      heap()->new_space()->set_end(mutator_thread_->end_);
+    }
+    mutator_thread_->top_ = 0;
+    mutator_thread_->end_ = 0;
     mutator_thread_ = NULL;
   }
   thread->isolate_ = NULL;