Refactor: Return true when checks succeed in ParseContext Instead of returning false when a check succeeds in ParseContext, return true. This is more intuitive and in line with conventions used elsewhere inside ANGLE. Also includes some minor other cleanup in ParseContext, like improved variable names and code structure especially when checking array element properties. This will make introducing arrays of arrays easier in the future. BUG=angleproject:911 TEST=angle_unittests Change-Id: I68233c01ccfbfef9529341af588f615efc2b503a Reviewed-on: https://chromium-review.googlesource.com/371238 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>