Add support for reading .gypi files.

tools/gn/parse_tree_unittest.cc

 // Copyright 2014 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 "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/test_with_scope.h"
 
@@ skipping 13 matching lines @@
       new IdentifierNode(member_token));
   accessor.set_member(member_identifier.Pass());
 
   // The access should fail because a is not defined.
   Err err;
   Value result = accessor.Execute(setup.scope(), &err);
   EXPECT_TRUE(err.has_error());
   EXPECT_EQ(Value::NONE, result.type());
 
   // Define a as a Scope. It should still fail because b isn't defined.
-  Scope a_scope(setup.scope());
   err = Err();
-  setup.scope()->SetValue("a", Value(NULL, &a_scope), NULL);
+  setup.scope()->SetValue("a",
+      Value(NULL, scoped_ptr<Scope>(new Scope(setup.scope()))), NULL);
   result = accessor.Execute(setup.scope(), &err);
   EXPECT_TRUE(err.has_error());
   EXPECT_EQ(Value::NONE, result.type());
 
   // Define b, accessor should succeed now.
   const int64 kBValue = 42;
   err = Err();
-  a_scope.SetValue("b", Value(NULL, kBValue), NULL);
+  setup.scope()->GetMutableValue("a", false)->scope_value()->SetValue(
+      "b", Value(NULL, kBValue), NULL);
   result = accessor.Execute(setup.scope(), &err);
   EXPECT_FALSE(err.has_error());
   ASSERT_EQ(Value::INTEGER, result.type());
   EXPECT_EQ(kBValue, result.int_value());
 }