Remove unneeded GrGLSLTransformedCoordsArray type

Rename GrGLSLFragmentBuilder::ensureFSCoords2D to ensureCoords2D and make it take an arbitrary GrShaderVar.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2324663004

Review-Url: https://codereview.chromium.org/2324663004
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 78ecffa..1fbd171 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -333,7 +333,7 @@
     const GrRadialGradient& ge = args.fFp.cast<GrRadialGradient>();
     this->emitUniforms(args.fUniformHandler, ge);
     SkString t("length(");
-    t.append(args.fFragBuilder->ensureFSCoords2D(args.fCoords, 0));
+    t.append(args.fFragBuilder->ensureCoords2D(args.fTransformedCoords[0]));
     t.append(")");
     this->emitColor(args.fFragBuilder,
                     args.fUniformHandler,