Improve consistency of SPIR-V code generation.
Improve consistency of SPIR-V code generation.

The SPIR-V code generator would sometimes invoke helper functions in an
unsequenced way, causing the output to vary across different compilers
or optimization settings. This CL explicitly sequences these operations,
which should make the output consistent across platforms.

Change-Id: Iaaf75b80e7495768d73dd6afa5b6d03f9cf3f262
Bug: skia:11175
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/356844
Commit-Queue: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Commit-Queue: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>

aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia