Update guards in ShaderVariable.h. We neglected to update the text of the guards when we renamed the file from Uniform.h to ShaderVariable.h. BUG=angle:533 Change-Id: I59969113536b69a418cf233ef0d7dd797e666ea9 Reviewed-on: https://chromium-review.googlesource.com/180978 Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Reviewed-by: Nicolas Capens <nicolascapens@chromium.org> Commit-Queue: Nicolas Capens <nicolascapens@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>