Merge third_party/skia/gyp from https://chromium.googlesource.com/external/skia/gyp.git at 961f4e74a20aa05ef5a89b548b29a43a2edb7f42

This commit was generated by merge_from_chromium.py.

Change-Id: Ic813812cf8c641dbebab50fd739d3dcfbfceeccf