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 a18f181bef8ccb3e0ca80d43dc5a1f3107105d73..202d50d0063a23289c707d7cb1c066fbcda953c1 100644
--- a/src/contexts.cc
+++ b/src/contexts.cc
@@ -589,5 +589,27 @@ bool Context::IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object) {
 }
 #endif
 
+void Context::IncrementExceptionsThrown() {
+  if (!IsNativeContext()) return;

[jochen (gone - plz use gerrit), 2015/10/29 14:37:07]

just DCHECK(IsNativeContext())

[Michael Hablich, 2015/10/29 15:23:34]

Done.

+  if (exceptions_thrown()->IsUndefined()) {

[jochen (gone - plz use gerrit), 2015/10/29 14:37:07]

just initialize exceptions_thrown() to 0 in Factory::NewNativeContext

[Michael Hablich, 2015/10/29 15:23:34]

Done.

+    set_exceptions_thrown(Smi::FromInt(1));
+    return;
+  }
+
+  int previous_value = Smi::cast(exceptions_thrown())->value();
+  set_exceptions_thrown(Smi::FromInt(previous_value+1));
+}
+
+
+int Context::GetExceptionsThrown() {
+  // return -1 so we can identify stats by non-native contexts
+  if (!IsNativeContext()) return -1;

[jochen (gone - plz use gerrit), 2015/10/29 14:37:07]

should never happen

[Michael Hablich, 2015/10/29 15:23:34]

Done.

+  if (exceptions_thrown()->IsUndefined()) {
+    return 0;
+  }
+
+  return Smi::cast(exceptions_thrown())->value();
+}
+
 }  // namespace internal
 }  // namespace v8