Start implementing jdb "locals".

This lets us show the names and types of the locals, but all the values
will show up as 0/null. We're going to have to walk the whole stack and
take callee-save frames into account to do that right.

Change-Id: Ic6e115513b6e65ae7ed4b7274e70bc514e83190a
diff --git a/src/java_lang_Class.cc b/src/java_lang_Class.cc
index 1700ce1..1a625be 100644
--- a/src/java_lang_Class.cc
+++ b/src/java_lang_Class.cc
@@ -237,7 +237,7 @@
   Class* klass = Decode<Class*>(env, jklass);
   DCHECK(klass->IsClass());
   String* name = Decode<String*>(env, jname);
-  DCHECK(name->IsString());
+  DCHECK(name->GetClass()->IsStringClass());
 
   for (size_t i = 0; i < klass->NumInstanceFields(); ++i) {
     Field* f = klass->GetInstanceField(i);