Renamed ReferenceMapVisitor to prevent confusion with art version.

The test was using art::ReferenceMapVisitor by mistake somehow.

Change-Id: Ib509841b79240ff7753edca8238195db39b4c4a9
diff --git a/test/StackWalk/stack_walk_jni.cc b/test/StackWalk/stack_walk_jni.cc
index 95c7de6..15d866f 100644
--- a/test/StackWalk/stack_walk_jni.cc
+++ b/test/StackWalk/stack_walk_jni.cc
@@ -38,8 +38,8 @@
 
 static int gJava_StackWalk_refmap_calls = 0;
 
-struct ReferenceMapVisitor : public Thread::StackVisitor {
-  ReferenceMapVisitor() {
+struct TestReferenceMapVisitor : public Thread::StackVisitor {
+  TestReferenceMapVisitor() {
   }
 
   bool VisitFrame(const Frame& frame, uintptr_t pc) {
@@ -99,7 +99,7 @@
   gJava_StackWalk_refmap_calls++;
 
   // Visitor
-  ReferenceMapVisitor mapper;
+  TestReferenceMapVisitor mapper;
   Thread::Current()->WalkStack(&mapper);
 
   return count + 1;
@@ -109,7 +109,7 @@
   gJava_StackWalk_refmap_calls++;
 
   // Visitor
-  ReferenceMapVisitor mapper;
+  TestReferenceMapVisitor mapper;
   Thread::Current()->WalkStack(&mapper);
 
   return count + 1;