Revert "Revert "Revert "skia: Rename perf flag"" ...USE:"
	I only needed this to test setting var in build repo.
	It is better to try to keep all equal for mgrep etc.
This reverts commit 1c56efbeb0a91f05599b6cd366c78f7889c402ea.

Change-Id: If60865ce92287dcff638db29fa2b35fad9c23118