Reverted due to vm test failure.

runtime/vm/thread.h

Index: runtime/vm/thread.h
diff --git a/runtime/vm/thread.h b/runtime/vm/thread.h
index 6f3100279f926700f702e08d294bfaed0e5e1376..e3761cd753a50022c97d302acb52acf95dff8639 100644
--- a/runtime/vm/thread.h
+++ b/runtime/vm/thread.h
@@ -377,8 +377,6 @@ class Thread : public BaseThread {
   uword top() { return top_; }
   uword end() { return end_; }
 
-  bool HasActiveTLAB() { return end_ > 0; }
-
   static intptr_t top_offset() { return OFFSET_OF(Thread, top_); }
   static intptr_t end_offset() { return OFFSET_OF(Thread, end_); }