use Make instead of Create to return a shared shader

Partially updated call sites. Undefine the flag in SkSHader.h to convert the remaining sites.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1772463002

Review URL: https://codereview.chromium.org/1772463002
diff --git a/samplecode/SampleXfer.cpp b/samplecode/SampleXfer.cpp
index 221ba58..58546e1 100644
--- a/samplecode/SampleXfer.cpp
+++ b/samplecode/SampleXfer.cpp
@@ -127,10 +127,9 @@
 public:
     CircDrawable(SkScalar size, SkColor c) {
         const SkColor colors[] = { 0, c };
-        SkAutoTUnref<SkShader> shader(SkGradientShader::CreateRadial(SkPoint::Make(size/2, size/2), size/2,
+        fPaint.setShader(SkGradientShader::MakeRadial(SkPoint::Make(size/2, size/2), size/2,
                                                                      colors, nullptr, 2,
                                                                      SkShader::kClamp_TileMode));
-        fPaint.setShader(shader);
         fBounds = SkRect::MakeWH(size, size);
     }