Reland of "Finish conversion to sk_sp<SkShader> (patchset #2 id:20001 of https://codereview.chromium.org/1803763002/ )"

This reverts commit 106e10ddff5d473dc81dd1ce8ade615585ea609b.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1803783002
CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Release-CMake-Trybot,Build-Mac-Clang-x86_64-Release-CMake-Trybot

TBR=

Review URL: https://codereview.chromium.org/1803783002
diff --git a/samplecode/SampleClamp.cpp b/samplecode/SampleClamp.cpp
index e319a56..9739053 100644
--- a/samplecode/SampleClamp.cpp
+++ b/samplecode/SampleClamp.cpp
@@ -13,25 +13,20 @@
 #include "SkGradientShader.h"
 #include "SkPicture.h"
 
-static SkShader* make_linear() {
+static sk_sp<SkShader> make_linear() {
     SkPoint pts[] = { 0, 0, SK_Scalar1/500, SK_Scalar1/500 };
     SkColor colors[] = { SK_ColorRED, SK_ColorBLUE };
-    return SkGradientShader::CreateLinear(pts, colors, nullptr, 2,
-                                          SkShader::kClamp_TileMode);
+    return SkGradientShader::MakeLinear(pts, colors, nullptr, 2, SkShader::kClamp_TileMode);
 }
 
 class ClampView : public SampleView {
-    SkShader*   fGrad;
+    sk_sp<SkShader> fGrad;
 
 public:
     ClampView() {
         fGrad = make_linear();
     }
 
-    virtual ~ClampView() {
-        fGrad->unref();
-    }
-
 protected:
     // overrides from SkEventSink
     virtual bool onQuery(SkEvent* evt) {