Add support for unary plus in hydrogen compiler.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 6cb2b240a95b61103609b49d4f2532282985591d..41d54865969a05e7a46f02e7f01bd17d82534084 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -4519,7 +4519,7 @@ void HGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
       VisitForEffect(expr->expression());
     }
 
-  } else if (op == Token::BIT_NOT || op == Token::SUB) {
+  } else {
     VISIT_FOR_VALUE(expr->expression());
     HValue* value = Pop();
     HInstruction* instr = NULL;
@@ -4528,19 +4528,19 @@ void HGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
         instr = new HBitNot(value);
         break;
       case Token::SUB:
-        instr = new HMul(graph_->GetConstantMinus1(), value);
+        instr = new HMul(value, graph_->GetConstantMinus1());
+        break;
+      case Token::ADD:
+        instr = new HMul(value, graph_->GetConstant1());
+        break;
+      case Token::TYPEOF:
+        instr = new HTypeof(value);
         break;
       default:
-        UNREACHABLE();
+        BAILOUT("Value: unsupported unary operation");
         break;
     }
     ast_context()->ReturnInstruction(instr, expr->id());
-  } else if (op == Token::TYPEOF) {
-    VISIT_FOR_VALUE(expr->expression());
-    HValue* value = Pop();
-    ast_context()->ReturnInstruction(new HTypeof(value), expr->id());
-  } else {
-    BAILOUT("Value: unsupported unary operation");
   }
 }