Improve handling of unary plus.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 127d7a9aa1ed13943d558e7096ec35ca15ae3818..8bfc52efb63a57235e6539536216a2369d72858b 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -9160,7 +9160,6 @@ void HOptimizedGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
     case Token::DELETE: return VisitDelete(expr);
     case Token::VOID: return VisitVoid(expr);
     case Token::TYPEOF: return VisitTypeof(expr);
-    case Token::ADD: return VisitAdd(expr);
     case Token::SUB: return VisitSub(expr);
     case Token::BIT_NOT: return VisitBitNot(expr);
     case Token::NOT: return VisitNot(expr);
@@ -9218,21 +9217,6 @@ void HOptimizedGraphBuilder::VisitTypeof(UnaryOperation* expr) {
 }
 
 
-void HOptimizedGraphBuilder::VisitAdd(UnaryOperation* expr) {
-  CHECK_ALIVE(VisitForValue(expr->expression()));
-  HValue* value = Pop();
-  HValue* context = environment()->LookupContext();
-  HInstruction* instr =
-      HMul::New(zone(), context, value, graph()->GetConstant1());
-  if (instr->IsBinaryOperation()) {
-    // Since we don't have type feedback, we must be cautious/pessimistic.
-    HBinaryOperation::cast(instr)->set_observed_input_representation(
-        Representation::Tagged(), Representation::Tagged());
-  }
-  return ast_context()->ReturnInstruction(instr, expr->id());
-}
-
-
 void HOptimizedGraphBuilder::VisitSub(UnaryOperation* expr) {
   CHECK_ALIVE(VisitForValue(expr->expression()));
   HValue* value = Pop();