Fix and extend the documentation of art::Thread's fields offsets.

Change-Id: Ie13c71d1b734ec0778c388b9bcb7773dcf319f16
diff --git a/runtime/asm_support.h b/runtime/asm_support.h
index b1d0841..f4f8eaf 100644
--- a/runtime/asm_support.h
+++ b/runtime/asm_support.h
@@ -103,17 +103,20 @@
 ADD_TEST_EQ(THREAD_TOP_QUICK_FRAME_OFFSET,
             art::Thread::TopOfManagedStackOffset<__SIZEOF_POINTER__>().Int32Value())
 
-// Offset of field Thread::tlsPtr_.managed_stack.top_quick_frame_.
+// Offset of field Thread::tlsPtr_.self.
 #define THREAD_SELF_OFFSET (THREAD_CARD_TABLE_OFFSET + (9 * __SIZEOF_POINTER__))
 ADD_TEST_EQ(THREAD_SELF_OFFSET,
             art::Thread::SelfOffset<__SIZEOF_POINTER__>().Int32Value())
 
+// Offset of field Thread::tlsPtr_.thread_local_pos.
 #define THREAD_LOCAL_POS_OFFSET (THREAD_CARD_TABLE_OFFSET + 150 * __SIZEOF_POINTER__)
 ADD_TEST_EQ(THREAD_LOCAL_POS_OFFSET,
             art::Thread::ThreadLocalPosOffset<__SIZEOF_POINTER__>().Int32Value())
+// Offset of field Thread::tlsPtr_.thread_local_end.
 #define THREAD_LOCAL_END_OFFSET (THREAD_LOCAL_POS_OFFSET + __SIZEOF_POINTER__)
 ADD_TEST_EQ(THREAD_LOCAL_END_OFFSET,
             art::Thread::ThreadLocalEndOffset<__SIZEOF_POINTER__>().Int32Value())
+// Offset of field Thread::tlsPtr_.thread_local_objects.
 #define THREAD_LOCAL_OBJECTS_OFFSET (THREAD_LOCAL_POS_OFFSET + 2 * __SIZEOF_POINTER__)
 ADD_TEST_EQ(THREAD_LOCAL_OBJECTS_OFFSET,
             art::Thread::ThreadLocalObjectsOffset<__SIZEOF_POINTER__>().Int32Value())