[turbofan] Implemented the optional Float32RoundTruncate operator.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index cb9073afb531dc59e1bbcc11019e36b3ed2de1ee..b7f78b888b471544b3951f857543e1d93637d66d 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -2289,6 +2289,12 @@ Type* Typer::Visitor::TypeFloat64RoundUp(Node* node) {
 }
 
 
+Type* Typer::Visitor::TypeFloat32RoundTruncate(Node* node) {
+  // TODO(sigurds): We could have a tighter bound here.
+  return Type::Number();
+}
+
+
 Type* Typer::Visitor::TypeFloat64RoundTruncate(Node* node) {
   // TODO(sigurds): We could have a tighter bound here.
   return Type::Number();