Add savelayer_with_backdrop GM to benchmark

The performance regression only happened on iOS devices. Benchmarking
on Desktops or Android devices doesn't seem to show any significant
regressions.

Tested this on iPhone XS with nanobench and saw a 10ms->30ms regression:

regression:
  61/63  MB 1   10.5ms  10.7ms  10.8ms  12.2ms  5%  █▂▁▁▂▁▂▂▂▁  8888    GM_savelayer_with_backdrop
 101/101 MB 1   36ms    36.5ms  36.4ms  36.8ms  1%  ▁▅▃▆▆▄▆▃▃█  gles    GM_savelayer_with_backdrop

before regression:
  61/63  MB 1   10.3ms  10.4ms  10.6ms  12.4ms  6%  █▂▁▂▁▁▁▁▁▁  8888    GM_savelayer_with_backdrop
  96/96  MB 1   10.6ms  10.7ms  10.7ms  10.8ms  1%  ▄▁▄▂▆█▅▃▂▅  gles    GM_savelayer_with_backdrop

It's interesting to see that 8888 is always fast. Is the regressing CL changing blur from software to GPU?

Bug: https://github.com/flutter/flutter/issues/36064
Change-Id: Iea2305e41a31bd5b4267f45bfd835231d49d639a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/234413
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
1 file changed