Revert "Fix unused variable "useSwiftShader"" This reverts commit d721cdefdcf4c3e62ae364f0dc525e3ca54042a3. Reason for revert: missing include Original change's description: > Fix unused variable "useSwiftShader" > > -Wunused-but-set-variable when rolling into Chromium crrev.com/c/3293895 > > Bug: angleproject:6496 > Change-Id: I02f7de303b52319c6a1821d7b697b7ee9bea8f89 > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3292034 > Reviewed-by: Tim Van Patten <timvp@google.com> > Commit-Queue: Tim Van Patten <timvp@google.com> Bug: angleproject:6496 Change-Id: I12748620cc20348bbcbe0304609a19ab65052b0e No-Presubmit: true No-Tree-Checks: true No-Try: true Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3292035 Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>