Move the thread local functions to the Thread class in runtime/platform

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index e2c77fa0066167c8263fda45688a222fc1a48953..c4d7978da840dab96b4fe38a60670703368d081c 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -134,6 +134,21 @@ Isolate::~Isolate() {
   message_handler_ = NULL;  // Fail fast if we send messages to a dead isolate.
 }
 
+void Isolate::SetCurrent(Isolate* current) {
+  Thread::SetThreadLocal(isolate_key, reinterpret_cast<uword>(current));
+}
+
+
+ThreadLocalKey Isolate::isolate_key = Thread::kInvalidThreadLocal;
+
+
+void Isolate::InitOnce() {
+  ASSERT(isolate_key == Thread::kInvalidThreadLocal);
+  isolate_key = Thread::CreateThreadLocal();
+  ASSERT(isolate_key != Thread::kInvalidThreadLocal);
+  create_callback_ = NULL;
+}
+
 
 Isolate* Isolate::Init(const char* name_prefix) {
   Isolate* result = new Isolate();