[turbofan] Added the optional Float64RoundTiesEven operator to turbofan.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 8051784562b0a48543d2f5f4ac5fcf67e196ff75..f62fad6ed6c6a0ac9a474fbf9e76bde710ff7ff4 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -2252,6 +2252,12 @@ Type* Typer::Visitor::TypeFloat64RoundTiesAway(Node* node) {
 }
 
 
+Type* Typer::Visitor::TypeFloat64RoundTiesEven(Node* node) {
+  // TODO(sigurds): We could have a tighter bound here.
+  return Type::Number();
+}
+
+
 Type* Typer::Visitor::TypeFloat64ExtractLowWord32(Node* node) {
   return Type::Signed32();
 }