Implement new stacktrace and deoptimization stress testing flags:

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index d10bef9a2fd899fb83c032212b6206827cc3a69c..aa8f2a7aea9e05e1bb5b488caa1f01183744e13d 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -321,6 +321,8 @@ Isolate::Isolate()
       mutex_(new Mutex()),
       stack_limit_(0),
       saved_stack_limit_(0),
+      stack_overflow_flags_(0),
+      stack_overflow_count_(0),
       message_handler_(NULL),
       spawn_state_(NULL),
       is_runnable_(false),
@@ -662,6 +664,13 @@ uword Isolate::GetAndClearInterrupts() {
 }
 
 
+uword Isolate::GetAndClearStackOverflowFlags() {
+  uword stack_overflow_flags = stack_overflow_flags_;
+  stack_overflow_flags_ = 0;
+  return stack_overflow_flags;
+}
+
+
 static int MostUsedFunctionFirst(const Function* const* a,
                                  const Function* const* b) {
   if ((*a)->usage_counter() > (*b)->usage_counter()) {