Refactor common functionality out of draw call perf tests Common functionality across some perf tests is moved to a separate utility file, draw_call_perf_utils. This will make it simpler to add more perf tests, such as tests for multiview drawing. BUG=angleproject:1669 TEST=angle_perftests Change-Id: I2108d7425f7d8f43f333ea9daa6779e42862350b Reviewed-on: https://chromium-review.googlesource.com/422332 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>