Print message when throwing new exception with pending exception.

Useful to see what the new exception is.

Bug: 12957138
Change-Id: I751b3a9b0b5d57d72f15d3ed7fa746a1991b181c
diff --git a/runtime/thread.h b/runtime/thread.h
index 9813130..f9d31af 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -285,6 +285,7 @@
   }
 
   void AssertNoPendingException() const;
+  void AssertNoPendingExceptionForNewException(const char* msg) const;
 
   void SetException(const ThrowLocation& throw_location, mirror::Throwable* new_exception)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {