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..b54f9f5a73f5eb412517a1af9d9929b4e8948c56 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;

[rmacnak, 2017/07/05 17:39:52]

// Grab an allocation area.

[danunez, 2017/07/05 18:12:55]

Done.

+      if (this != Dart::vm_isolate()) {

[rmacnak, 2017/07/05 17:39:52]

Is there a property of the heap we can check instead? Perhaps a zero-sized
new-space?

[danunez, 2017/07/05 18:12:55]

That should work. I'll give it a shot.

+        mutator_thread_->top_ = *(heap()->new_space()->TopAddress());

[rmacnak, 2017/07/05 17:39:52]

*top_address() -> top()

[danunez, 2017/07/05 18:12:55]

Done.

+        mutator_thread_->end_ = *(heap()->new_space()->EndAddress());
+      }
     }
     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()) {

[rmacnak, 2017/07/05 17:39:52]

// Release allocation area.

[danunez, 2017/07/05 18:12:55]

Done.

+      *(heap()->new_space()->TopAddress()) = mutator_thread_->top_;

[rmacnak, 2017/07/05 17:39:52]

*top_address() -> set_top()

[danunez, 2017/07/05 18:12:55]

Done.

+      *(heap()->new_space()->EndAddress()) = mutator_thread_->end_;
+    }
+    mutator_thread_->top_ = 0;
+    mutator_thread_->end_ = 0;
     mutator_thread_ = NULL;
   }
   thread->isolate_ = NULL;