Provide a counter for thrown JavaScript errors per context

src/contexts.cc

Index: src/contexts.cc
diff --git a/src/contexts.cc b/src/contexts.cc
index 9da13fe9e8a00665090f207aa7c6d7066d234bb4..67d19a1eff96a8ac2f8ea7b66fac3a56b253f65a 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -577,5 +577,16 @@ bool Context::IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object) {
 }
 #endif
 
+
+void Context::IncrementErrorsThrown() {
+  DCHECK(IsNativeContext());
+
+  int previous_value = errors_thrown()->value();
+  set_errors_thrown(Smi::FromInt(previous_value + 1));
+}
+
+
+int Context::GetErrorsThrown() { return errors_thrown()->value(); }
+
 }  // namespace internal
 }  // namespace v8