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/SampleXfermodesBlur.cpp b/samplecode/SampleXfermodesBlur.cpp
index f995c6a..63c90fe 100644
--- a/samplecode/SampleXfermodesBlur.cpp
+++ b/samplecode/SampleXfermodesBlur.cpp
@@ -150,10 +150,8 @@
         const SkScalar h = SkIntToScalar(H);
         SkMatrix m;
         m.setScale(SkIntToScalar(6), SkIntToScalar(6));
-        SkShader* s = SkShader::CreateBitmapShader(fBG,
-                                                   SkShader::kRepeat_TileMode,
-                                                   SkShader::kRepeat_TileMode,
-                                                   &m);
+        auto s = SkShader::MakeBitmapShader(fBG, SkShader::kRepeat_TileMode,
+                                            SkShader::kRepeat_TileMode, &m);
 
         SkPaint labelP;
         labelP.setAntiAlias(true);