[turbofan] Add Symbol feedback to Equal/StrictEqual.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index f92d507dfbc3bdb3dcaf09af48aed3e02d1449c3..363dad65d29b9ce08f70e248165c2634692b2d83 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1860,6 +1860,11 @@ Type* Typer::Visitor::TypeCheckString(Node* node) {
   return Type::Intersect(arg, Type::String(), zone());
 }
 
+Type* Typer::Visitor::TypeCheckSymbol(Node* node) {
+  Type* arg = Operand(node, 0);
+  return Type::Intersect(arg, Type::Symbol(), zone());
+}
+
 Type* Typer::Visitor::TypeCheckFloat64Hole(Node* node) {
   return typer_->operation_typer_.CheckFloat64Hole(Operand(node, 0));
 }