ART: Add missing namespace comments

Add closing namespace comments.

Bug: 32619234
Test: m
Change-Id: I1f50e09dcd1038c4b540b87e5c19e319c1f592e4
diff --git a/compiler/compiler.h b/compiler/compiler.h
index 908d366..cd4c591 100644
--- a/compiler/compiler.h
+++ b/compiler/compiler.h
@@ -25,11 +25,11 @@
 
 namespace jit {
   class JitCodeCache;
-}
+}  // namespace jit
 namespace mirror {
   class ClassLoader;
   class DexCache;
-}
+}  // namespace mirror
 
 class ArtMethod;
 class CompilerDriver;