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..797953bbfef03322d6ccd861ec90d2fae868107d 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -2658,6 +2658,8 @@ Thread* Isolate::ScheduleThread(bool is_mutator, bool bypass_safepoint) {
     thread->isolate_ = this;
     ASSERT(heap() != NULL);
     thread->heap_ = heap();
+    thread->top_ = *(heap()->new_space()->TopAddress());

[rmacnak, 2017/06/22 22:31:50]

Since we don't yet have background new-space allocation, only the mutator thread
should copy top from the semispace, and the helper threads should have 0s so
allocation fails.

[danunez, 2017/06/30 20:35:57]

Done.

+    thread->end_ = *(heap()->new_space()->EndAddress());
     thread->set_os_thread(os_thread);
     ASSERT(thread->execution_state() == Thread::kThreadInNative);
     thread->set_execution_state(Thread::kThreadInVM);