Fix to use a new context when verifying the stack.

(cherry picked from commit 19ff5e52f1409838a505c7f63fd57604c3b48fb3)

Change-Id: I45e8cc09a81d41b250a4496e2d010746b208a715
diff --git a/src/thread.cc b/src/thread.cc
index f15bfd5..ce81a8b 100644
--- a/src/thread.cc
+++ b/src/thread.cc
@@ -1734,8 +1734,8 @@
 }
 
 void Thread::VerifyStack() {
-  Context* context = GetLongJumpContext();
-  ReferenceMapVisitor mapper(context, VerifyObject, NULL);
+  UniquePtr<Context> context(Context::Create());
+  ReferenceMapVisitor mapper(context.get(), VerifyObject, NULL);
   WalkStack(&mapper);
 }
 #endif