Reland of "more shader-->sp conversions (patchset #5 id:80001 of https://codereview.chromium.org/1789633002/ )"

This reverts commit 9283d20afc27571f7a871d1bd1100dd5df584941.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1793303002

Review URL: https://codereview.chromium.org/1793303002
diff --git a/gm/rectangletexture.cpp b/gm/rectangletexture.cpp
index 20f2ead..4bdb4c9 100644
--- a/gm/rectangletexture.cpp
+++ b/gm/rectangletexture.cpp
@@ -42,14 +42,14 @@
         SkCanvas canvas(bmp);
         SkPoint pts[] = { {0, 0}, {0, SkIntToScalar(height)} };
         SkColor colors0[] = { 0xFF1060B0 , 0xFF102030 };
-        paint.setShader(SkGradientShader::CreateLinear(pts, colors0, nullptr, 2,
-                                                       SkShader::kClamp_TileMode))->unref();
+        paint.setShader(SkGradientShader::MakeLinear(pts, colors0, nullptr, 2,
+                                                     SkShader::kClamp_TileMode));
         canvas.drawPaint(paint);
 
         SkColor colors1[] = { 0xFFA07010 , 0xFFA02080 };
         paint.setAntiAlias(true);
-        paint.setShader(SkGradientShader::CreateLinear(pts, colors1, nullptr, 2,
-                                                       SkShader::kClamp_TileMode))->unref();
+        paint.setShader(SkGradientShader::MakeLinear(pts, colors1, nullptr, 2,
+                                                     SkShader::kClamp_TileMode));
         canvas.drawCircle(SkIntToScalar(width) / 2, SkIntToScalar(height) / 2,
                           SkIntToScalar(width + height) / 5, paint);
     }