Remove default value checking in GN, adds getenv function, reorders parameters to rebase_path.

tools/gn/value.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/value.h"
 
 #include "base/strings/string_number_conversions.h"
 
 Value::Value()
     : type_(NONE),
+      boolean_value_(false),
       int_value_(0),
       origin_(NULL) {
 }
 
 Value::Value(const ParseNode* origin, Type t)
     : type_(t),
+      boolean_value_(false),
       int_value_(0),
       origin_(origin) {
 }
 
 Value::Value(const ParseNode* origin, bool bool_val)
     : type_(BOOLEAN),
       boolean_value_(bool_val),
       int_value_(0),
       origin_(origin) {
 }
 
 Value::Value(const ParseNode* origin, int64 int_val)
     : type_(INTEGER),
       boolean_value_(false),
       int_value_(int_val),
       origin_(origin) {
 }
 
 Value::Value(const ParseNode* origin, std::string str_val)
     : type_(STRING),
       string_value_(),
+      boolean_value_(false),
       int_value_(0),
       origin_(origin) {
   string_value_.swap(str_val);
 }
 
 Value::Value(const ParseNode* origin, const char* str_val)
     : type_(STRING),
       string_value_(str_val),
+      boolean_value_(false),
       int_value_(0),
       origin_(origin) {
 }
 
 Value::~Value() {
 }
 
 void Value::RecursivelySetOrigin(const ParseNode* origin) {
   set_origin(origin);
   if (type_ == Value::LIST) {
@@ skipping 75 matching lines @@
       }
       return true;
     default:
       return false;
   }
 }
 
 bool Value::operator!=(const Value& other) const {
   return !operator==(other);
 }