Add missing SHARED_LOCKS_REQUIRED attibute.

BUG: 18093707
Change-Id: I66e5c7650c67bb308472ff0da7faed6dff4ead53
diff --git a/runtime/arch/arm64/context_arm64.h b/runtime/arch/arm64/context_arm64.h
index 7b6aac9..d9a433b 100644
--- a/runtime/arch/arm64/context_arm64.h
+++ b/runtime/arch/arm64/context_arm64.h
@@ -34,7 +34,7 @@
 
   void Reset() OVERRIDE;
 
-  void FillCalleeSaves(const StackVisitor& fr) OVERRIDE;
+  void FillCalleeSaves(const StackVisitor& fr) OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void SetSP(uintptr_t new_sp) OVERRIDE {
     bool success = SetGPR(SP, new_sp);