Add support for substring replacement in gypi_to_gn

Use substring replacement in skia source file list, and update the skia BUILD.gn file accordingly. The .gn file gets a bit simpler now: we can do the substring replacement to make absolute paths rather than doing rebase for all the files.

[email protected], [email protected]

Review URL: https://codereview.chromium.org/231983002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@263272 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed