Chris Bracken dc4ecd943b Use iOS scale when computing render buffer size (#4171) (flutter/engine#4373)
When checking whether render buffer size has changed, apply the device
scale factor used to convert points to pixels to ensure we're not
needlessly re-allocating render buffer storage.

Adds trace + debug log to make this easier to detect in future.

Originally introduced in 72c28f3a01bd9e6bed256edc4629705d96a7cead, but
rolled back in d539abd7c5fe5291bab81b32e6e5697c1b6681b6 to test whether
it was responsible for regressions to
flutter_gallery_ios__transition_perf benchmarks:
  * average_frame_build_time_millis
  * missed_frame_build_budget_count

Re-landed in 1a7ca91e3938abd5720b3553dfb2045a6b805a3b, and reverted in
79b9bdbbf4d3193620be35e3ea3e1a162b553627 after it appeared to regress
the above two benchmarks. After recent changes to microtask execution
order which fixed https://github.com/flutter/flutter/issues/9998,
re-introducing this fix results in benchmark improvements to the above
two benchmarks in local testing.
2017-11-20 14:15:26 -08:00
..