Fix determining of JS lower stack bottom used in profiler's JS stack tracer to work with Chromium.

src/top.cc

Index: src/top.cc
diff --git a/src/top.cc b/src/top.cc
index b2583dbcbac1941274c6e67e50fd82d121b3bea0..68d01cfb786a038b536f4721fae9335aec6cd28c 100644
--- a/src/top.cc
+++ b/src/top.cc
@@ -91,6 +91,9 @@ void Top::Iterate(ObjectVisitor* v) {
 void Top::InitializeThreadLocal() {
   thread_local_.c_entry_fp_ = 0;
   thread_local_.handler_ = 0;
+#ifdef ENABLE_LOGGING_AND_PROFILING
+  thread_local_.js_entry_sp_ = 0;
+#endif
   thread_local_.stack_is_cooked_ = false;
   thread_local_.try_catch_handler_ = NULL;
   thread_local_.context_ = NULL;