Increase use of ScopedJniThreadState.

Move the routines for changing Object* to jobject and vice-versa
(AddLocalReference and Decode) to ScopedJniThreadState to enforce use of
Object*s in the Runnable thread state. In the Runnable thread state
suspension is necessary before GC can take place.

Reduce use of const ClassLoader* as the code bottoms out in FindClass
and with a field assignment where the const is cast away (ie if we're
not going to enforce the const-ness we shouldn't pretend it is).

Refactor the Thread::Attach API so that we're not handling raw Objects on
unattached threads.

Remove some unreachable code.

Change-Id: I0fa969f49ee6a8f10752af74a6b0e04d46b4cd97
diff --git a/src/jdwp/jdwp_main.cc b/src/jdwp/jdwp_main.cc
index 3a4d398..dfe83ff 100644
--- a/src/jdwp/jdwp_main.cc
+++ b/src/jdwp/jdwp_main.cc
@@ -270,7 +270,7 @@
 
 void JdwpState::Run() {
   Runtime* runtime = Runtime::Current();
-  runtime->AttachCurrentThread("JDWP", true, Thread::GetSystemThreadGroup());
+  runtime->AttachCurrentThread("JDWP", true, runtime->GetSystemThreadGroup());
 
   VLOG(jdwp) << "JDWP: thread running";