Fix race in debug assertion.

Change order of initialization for the two-way pointers between Isolate and Thread.

This only affects the debug assertion in Isolate::mutator_thread().

R=iposva@google.com

Review URL: https://codereview.chromium.org//1138643006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@45814 260f80e4-7a28-3924-810f-c04153c831b5
diff --git a/dart/runtime/vm/thread.cc b/dart/runtime/vm/thread.cc
index 19fb167..693dd9a 100644
--- a/dart/runtime/vm/thread.cc
+++ b/dart/runtime/vm/thread.cc
@@ -51,6 +51,7 @@
   Thread* thread = Thread::Current();
   ASSERT(thread->isolate() == NULL);
   ASSERT(isolate->mutator_thread() == NULL);
+  thread->isolate_ = isolate;
   isolate->set_mutator_thread(thread);
   // TODO(koda): Migrate thread_state_ and profile_data_ to Thread, to allow
   // helper threads concurrent with mutator.
@@ -64,7 +65,6 @@
   Profiler::BeginExecution(isolate);
   isolate->set_thread_state(thread_state);
   isolate->set_vm_tag(VMTag::kVMTagId);
-  thread->isolate_ = isolate;
 }