A couple optimizations to Metal Shader Pipeline
A couple optimizations to Metal Shader Pipeline

- Don't create an empty options object just to destroy it.
- Don't copy the shader source into the NSString.
- Allow UTF-8 shader source, not just ASCII.

Change-Id: Ic15ba5d315e42875e6db43af086c23a905c1dac4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/312837
Commit-Queue: Adlai Holler <74c8d5b16bacf4a5997d6535bb4043bbdfe052ea@google.com>
Reviewed-by: Jim Van Verth <509afb0bfbb23ecaaf1fb3323209f531b45e75a6@google.com>
Reviewed-by: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>

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