Add missing OVERRIDE qualifiers in code generators.

Test: mmma art
Change-Id: I91d0a2dc23dc8d63a9bb3607eb1c1517eabaeb1f
diff --git a/compiler/optimizing/code_generator_arm.h b/compiler/optimizing/code_generator_arm.h
index ce9d7e6..38a2410 100644
--- a/compiler/optimizing/code_generator_arm.h
+++ b/compiler/optimizing/code_generator_arm.h
@@ -556,10 +556,10 @@
   // artReadBarrierForRootSlow.
   void GenerateReadBarrierForRootSlow(HInstruction* instruction, Location out, Location root);
 
-  void GenerateNop();
+  void GenerateNop() OVERRIDE;
 
-  void GenerateImplicitNullCheck(HNullCheck* instruction);
-  void GenerateExplicitNullCheck(HNullCheck* instruction);
+  void GenerateImplicitNullCheck(HNullCheck* instruction) OVERRIDE;
+  void GenerateExplicitNullCheck(HNullCheck* instruction) OVERRIDE;
 
  private:
   Register GetInvokeStaticOrDirectExtraParameter(HInvokeStaticOrDirect* invoke, Register temp);