gn format: support absolute file system paths

tools/gn/command_format_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 "base/files/file_util.h"
 #include "base/strings/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/commands.h"
+#include "tools/gn/setup.h"
 
 namespace commands {
-bool FormatFileToString(const std::string& input_filename,
+bool FormatFileToString(Setup* setup,
+                        const SourceFile& file,
                         bool dump_tree,
                         std::string* output);
 }  // namespace commands
 
 #define FORMAT_TEST(n)                                                 \
   TEST(Format, n) {                                                    \
+    ::Setup setup;                                                     \
     std::string out;                                                   \
     std::string expected;                                              \
     EXPECT_TRUE(commands::FormatFileToString(                          \
-        "//tools/gn/format_test_data/" #n ".gn", false, &out));        \
+        &setup,                                                        \
+        SourceFile("//tools/gn/format_test_data/" #n ".gn"),           \
+        false,                                                         \
+        &out));                                                        \
     ASSERT_TRUE(base::ReadFileToString(                                \
         base::FilePath(FILE_PATH_LITERAL("tools/gn/format_test_data/") \
                            FILE_PATH_LITERAL(#n)                       \
                                FILE_PATH_LITERAL(".golden")),          \
         &expected));                                                   \
     EXPECT_EQ(expected, out);                                          \
   }
 
 // These are expanded out this way rather than a runtime loop so that
 // --gtest_filter works as expected for individual test running.
@@ skipping 12 matching lines @@
 FORMAT_TEST(013)
 FORMAT_TEST(014)
 FORMAT_TEST(015)
 // TODO(scottmg): Requires precedence/parentheses FORMAT_TEST(016)
 FORMAT_TEST(017)
 FORMAT_TEST(018)
 FORMAT_TEST(019)
 FORMAT_TEST(020)
 FORMAT_TEST(021)
 FORMAT_TEST(022)