Attempts to fix bugs introduced in 8b6fcf50e85d.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 6c3fa50322b6ed43d2e7a8c7b3a81b17a484ccac..55720c97d681dcebdbff57a779d9c3dc8158d180 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -2574,9 +2574,10 @@ 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());
+      if ((Dart::vm_isolate() != NULL) &&
+          (heap() != Dart::vm_isolate()->heap())) {
+        mutator_thread_->set_top(0);
+        mutator_thread_->set_end(0);
       }
     }
     Thread::SetCurrent(thread);
@@ -2616,12 +2617,13 @@ 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_);
+    if ((Dart::vm_isolate() != NULL) &&
+        (heap() != Dart::vm_isolate()->heap())) {
+      if (mutator_thread_->HasActiveTLAB()) {
+        heap()->AbandonRemainingTLAB(mutator_thread_);
+      }
     }
-    mutator_thread_->top_ = 0;
-    mutator_thread_->end_ = 0;
+    ASSERT(!mutator_thread_->HasActiveTLAB());
     mutator_thread_ = NULL;
   }
   thread->isolate_ = NULL;