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

runtime/platform/thread_win.h

Index: runtime/platform/thread_win.h
diff --git a/runtime/platform/thread_win.h b/runtime/platform/thread_win.h
index daa75e4d8cc602f2d0c28a3bd800a12adb4b3f15..52551832803eb1ee3a9947cefb830d0abfed19be 100644
--- a/runtime/platform/thread_win.h
+++ b/runtime/platform/thread_win.h
@@ -13,6 +13,26 @@
 
 namespace dart {
 
+typedef DWORD ThreadLocalKey;
+
+class ThreadInlineImpl {
+ private:
+  ThreadInlineImpl() {}
+  ~ThreadInlineImpl() {}
+
+  static uword GetThreadLocal(ThreadLocalKey key) {
+    static ThreadLocalKey kUnsetThreadLocalKey = TLS_OUT_OF_INDEXES;
+    ASSERT(key != kUnsetThreadLocalKey);
+    return reinterpret_cast<uword>(TlsGetValue(key));
+  }
+
+  friend class Thread;
+
+  DISALLOW_ALLOCATION();
+  DISALLOW_COPY_AND_ASSIGN(ThreadInlineImpl);
+};
+
+
 class MutexData {
  private:
   MutexData() {}