[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index c4dc3182ef3b86424ade6581e9140b320b932d9f..4404d94e152a5188243f149e30ba0e232fb40266 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -2265,6 +2265,12 @@ Type* Typer::Visitor::TypeFloat64LessThanOrEqual(Node* node) {
 }
 
 
+Type* Typer::Visitor::TypeFloat32RoundDown(Node* node) {
+  // TODO(sigurds): We could have a tighter bound here.
+  return Type::Number();
+}
+
+
 Type* Typer::Visitor::TypeFloat64RoundDown(Node* node) {
   // TODO(sigurds): We could have a tighter bound here.
   return Type::Number();