The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/36773f30d94495bc81193a52b49504d2e137b9e3

commit 36773f30d94495bc81193a52b49504d2e137b9e3
Author: Pawel Pluciennik <ppluciennik@opera.com>
Date: Tue Mar 13 02:00:05 2018

Improved GN code related to resolving paths.

Moved most of the logic related to resolving paths
to ResolvePath and ResolveRelative in filesystem_utils.cc.
Improved SourceDir class to return std::string with resolved path
for cases when returning SourceDir or SourceFile wasn't really needed.

R=brettw@chromium.org, dpranke@chromium.org

Bug: 819720
Change-Id: Ia59da00e83de45431762ebb19a9153471f7e91e3
Reviewed-on: https://chromium-review.googlesource.com/953422
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542692}
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/build_settings.cc
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/build_settings.h
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/filesystem_utils.cc
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/filesystem_utils.h
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/function_exec_script.cc
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/function_get_path_info.cc
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/source_dir.cc
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/source_dir.h
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/source_file.cc
[modify] https://crrev.com/36773f30d94495bc81193a52b49504d2e137b9e3/tools/gn/target_generator.cc