remove SkColorSpaceXformSteps::Required

It's error-prone, and now unused.

Change-Id: Ibae848bdb121695521e66d6e8544a82678e22f7c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257660
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/src/core/SkColorSpaceXformSteps.cpp b/src/core/SkColorSpaceXformSteps.cpp
index c15fb9a..37f9364 100644
--- a/src/core/SkColorSpaceXformSteps.cpp
+++ b/src/core/SkColorSpaceXformSteps.cpp
@@ -12,14 +12,6 @@
 
 // TODO(mtklein): explain the logic of this file
 
-bool SkColorSpaceXformSteps::Required(SkColorSpace* src, SkColorSpace* dst) {
-    // Any SkAlphaType will work fine here as long as we use the same one.
-    SkAlphaType at = kPremul_SkAlphaType;
-    return 0 != SkColorSpaceXformSteps(src, at,
-                                       dst, at).flags.mask();
-    // TODO(mtklein): quicker impl. that doesn't construct an SkColorSpaceXformSteps?
-}
-
 SkColorSpaceXformSteps::SkColorSpaceXformSteps(SkColorSpace* src, SkAlphaType srcAT,
                                                SkColorSpace* dst, SkAlphaType dstAT) {
     // Opaque outputs are treated as the same alpha type as the source input.
diff --git a/src/core/SkColorSpaceXformSteps.h b/src/core/SkColorSpaceXformSteps.h
index 500fc2a..e470885 100644
--- a/src/core/SkColorSpaceXformSteps.h
+++ b/src/core/SkColorSpaceXformSteps.h
@@ -15,9 +15,6 @@
 class SkRasterPipeline;
 
 struct SkColorSpaceXformSteps {
-    // Returns true if SkColorSpaceXformSteps must be applied
-    // to draw content in `src` into a destination in `dst`.
-    static bool Required(SkColorSpace* src, SkColorSpace* dst);
 
     struct Flags {
         bool unpremul         = false;