Better testing of SkCodec to 565
Better testing of SkCodec to 565

If getPixels returns an unexpected result, do not create a digest
and compare it to digests for premul and unpremul.

Print a better error message, including the name of the image and
string versions of the SkCodec::Result.

Change-Id: Ie98e350a1ef91c0745fe9de0855192e5793e033c
Reviewed-on: https://skia-review.googlesource.com/c/176582
Auto-Submit: Leon Scroggins <995cad867ca30d6399abe011583a53547c8afea1@google.com>
Reviewed-by: Nigel Tao <58ae08b3356928ff9c67562b4719487d54fe8348@google.com>
Commit-Queue: Leon Scroggins <995cad867ca30d6399abe011583a53547c8afea1@google.com>

Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,HalCanary/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,HalCanary/skia-hc,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,google/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,HalCanary/skia-hc,HalCanary/skia-hc,aosp-mirror/platform_external_skia,rubenvb/skia,google/skia,HalCanary/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,google/skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,rubenvb/skia,HalCanary/skia-hc