Move no_callback_scope_depth_ and cha_ from isolate -> thread

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index f431dfdd4ce35779c608466a57aecb60389c33e7..9acc4615f1a99af2ae21b1ed4138083c8a6f7a67 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -195,6 +195,8 @@ Thread::Thread(bool init_vm_constants)
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_INITIALIZERS)
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_SCOPE_INIT)
       reusable_handles_(),
+      cha_(NULL),
+      no_callback_scope_depth_(0),
       thread_list_next_(NULL) {
   ClearState();
 
@@ -396,13 +398,13 @@ void Thread::StoreBufferAcquire() {
 
 CHA* Thread::cha() const {
   ASSERT(isolate_ != NULL);
-  return isolate_->cha_;
+  return cha_;
 }
 
 
 void Thread::set_cha(CHA* value) {
   ASSERT(isolate_ != NULL);
-  isolate_->cha_ = value;
+  cha_ = value;
 }