Skia color space fuzzer: mix input and output color transform formats

The fuzzer color transform had the same input and output pixel color
format in each run. In this change, create a mix of input and output
color formats to add extra fuzz.

Tbr: mmoroz@chromium.org
Bug: 708016
Change-Id: I520eafad1959ae2d8688b156e24006718aaf4b0c
Reviewed-on: https://chromium-review.googlesource.com/572890Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487026}

testing/libfuzzer/fuzzers/skia_color_space_fuzzer.cc

@@ -37,10 +37,11 @@ static void ColorTransform(size_t hash, bool input) {
 
   static uint32_t output[kPixels * 4];
 
-  const auto color = SkColorSpaceXform::ColorFormat(hash & 7);
-  const auto alpha = SkAlphaType(hash >> 3 & 3);
+  const auto form1 = SkColorSpaceXform::ColorFormat(hash >> 0 & 7);
+  const auto form2 = SkColorSpaceXform::ColorFormat(hash >> 3 & 7);
+  const auto alpha = SkAlphaType(hash >> 6 & 3);
 
-  transform->apply(color, output, color, pixels, kPixels, alpha);
+  transform->apply(form1, output, form2, pixels, kPixels, alpha);
 }
 
 static sk_sp<SkColorSpace> SelectProfile(size_t hash) {