gn: Support build directories outside the source tree.

tools/gn/label_unittest.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 "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/err.h"
 #include "tools/gn/label.h"
 #include "tools/gn/value.h"
 
 namespace {
@@ skipping 51 matching lines @@
   };
 
   Label default_toolchain(SourceDir("//t/"), "d");
 
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(cases); i++) {
     const ParseDepStringCase& cur = cases[i];
 
     std::string location, name;
     Err err;
     Value v(NULL, Value::STRING);
+    base::FilePath source_root("/source/root");
     v.string_value() = cur.str;
-    Label result =
-        Label::Resolve(SourceDir(cur.cur_dir), default_toolchain, v, &err);
+    Label result = Label::Resolve(SourceDir(cur.cur_dir), default_toolchain, v,
+                                  source_root, &err);
     EXPECT_EQ(cur.success, !err.has_error()) << i << " " << cur.str;
     if (!err.has_error() && cur.success) {
       EXPECT_EQ(cur.expected_dir, result.dir().value())
           << i << " " << cur.str;
       EXPECT_EQ(cur.expected_name, result.name())
           << i << " " << cur.str;
       EXPECT_EQ(cur.expected_toolchain_dir,
                 result.toolchain_dir().value())
           << i << " " << cur.str;
       EXPECT_EQ(cur.expected_toolchain_name, result.toolchain_name())
           << i << " " << cur.str;
     }
   }
 }