Create special surfaces according to original device (not always in N32)

src/effects/SkDisplacementMapEffect.cpp

Index: src/effects/SkDisplacementMapEffect.cpp
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index 8d068072a7454dd0f1f914ecdcae587d86b815f7..4f6386d92e94c478bf3bca6938768fd5a46a48a0 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -279,7 +279,18 @@ sk_sp<SkSpecialImage> SkDisplacementMapEffect::onFilterImage(SkSpecialImage* sou
     }
 
     SkIPoint displOffset = SkIPoint::Make(0, 0);
-    sk_sp<SkSpecialImage> displ(this->filterInput(0, source, ctx, &displOffset));
+    // Creation of the displacement map should happen in a non-colorspace aware context. This
+    // texture is a purely mathematical construct, so we want to just operate on the stored
+    // values. Consider:
+    // User supplies an sRGB displacement map. If we're rendering to a wider gamut, then we could
+    // end up filtering the displacement map into that gamut, which has the effect of reducing
+    // the amount of displacement that it represents (as encoded values move away from the
+    // primaries).
+    // With a more complex DAG attached to this input, it's not clear that working in ANY specific
+    // color space makes sense, so we ignore color spaces (and gamma) entirely. This may not be
+    // ideal, but it's at least consistent and predictable.
+    Context displContext(ctx.ctm(), ctx.clipBounds(), ctx.cache(), OutputProperties(nullptr));
+    sk_sp<SkSpecialImage> displ(this->filterInput(0, source, displContext, &displOffset));
     if (!displ) {
         return nullptr;
     }