Address some review comments

Addressed comments in dex cache and class table. Added class table
test.

Test: mm test-art-host-gtest-class_table_test -j20

Change-Id: I3ec0282247187acb1ec7af25b309501f001a1c3e
diff --git a/runtime/Android.bp b/runtime/Android.bp
index 08be5b2..32ebee2 100644
--- a/runtime/Android.bp
+++ b/runtime/Android.bp
@@ -517,6 +517,7 @@
         "base/unix_file/fd_file_test.cc",
         "cha_test.cc",
         "class_linker_test.cc",
+        "class_table_test.cc",
         "compiler_filter_test.cc",
         "dex_file_test.cc",
         "dex_file_verifier_test.cc",