partial switch over to sp usage of shaders

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1776973003

Review URL: https://codereview.chromium.org/1776973003
diff --git a/gm/blurrect.cpp b/gm/blurrect.cpp
index 55c592b..0fe866f 100644
--- a/gm/blurrect.cpp
+++ b/gm/blurrect.cpp
@@ -58,7 +58,7 @@
 /*
  * Spits out a dummy gradient to test blur with shader on paint
  */
-static SkShader* MakeRadial() {
+static sk_sp<SkShader> MakeRadial() {
     SkPoint pts[2] = {
         { 0, 0 },
         { SkIntToScalar(100), SkIntToScalar(100) }
@@ -74,10 +74,10 @@
                 SkScalarAve(pts[0].fY, pts[1].fY));
     center1.set(SkScalarInterp(pts[0].fX, pts[1].fX, SkIntToScalar(3)/5),
                 SkScalarInterp(pts[0].fY, pts[1].fY, SkIntToScalar(1)/4));
-    return SkGradientShader::CreateTwoPointConical(center1, (pts[1].fX - pts[0].fX) / 7,
-                                                  center0, (pts[1].fX - pts[0].fX) / 2,
-                                                  colors, pos, SK_ARRAY_COUNT(colors), tm,
-                                                  0, &scale);
+    return SkGradientShader::MakeTwoPointConical(center1, (pts[1].fX - pts[0].fX) / 7,
+                                                 center0, (pts[1].fX - pts[0].fX) / 2,
+                                                 colors, pos, SK_ARRAY_COUNT(colors), tm,
+                                                 0, &scale);
 }
 
 typedef void (*PaintProc)(SkPaint*, SkScalar width);
@@ -123,7 +123,7 @@
                 paint.setAlpha(fAlpha);
 
                 SkPaint paintWithRadial = paint;
-                paintWithRadial.setShader(MakeRadial())->unref();
+                paintWithRadial.setShader(MakeRadial());
 
                 static const Proc procs[] = {
                     fill_rect, draw_donut, draw_donut_skewed