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/stack.h b/src/stack.h
index bd0aee6..243ca28 100644
--- a/src/stack.h
+++ b/src/stack.h
@@ -31,9 +31,10 @@
 class Method;
 class Object;
 class ShadowFrame;
+class ScopedJniThreadState;
 class Thread;
 
-jobject GetThreadStack(JNIEnv*, Thread*);
+jobject GetThreadStack(const ScopedJniThreadState&, Thread*);
 
 class ShadowFrame {
  public: