use Make instead of Create to return a shared shader

src/core/SkComposeShader.h

Index: src/core/SkComposeShader.h
diff --git a/src/core/SkComposeShader.h b/src/core/SkComposeShader.h
index 9220a0de97ccbac9619558614caf96861af538f6..ee6e36a222b3a1161ecf971a0b203e48cac39af2 100644
--- a/src/core/SkComposeShader.h
+++ b/src/core/SkComposeShader.h
@@ -31,7 +31,7 @@ public:
         @param mode     The xfermode that combines the colors from the two shaders. If mode
                         is null, then SRC_OVER is assumed.
     */
-    SkComposeShader(SkShader* sA, SkShader* sB, SkXfermode* mode = NULL);
+    SkComposeShader(sk_sp<SkShader> sA, sk_sp<SkShader> sB, SkXfermode* mode = NULL);
     virtual ~SkComposeShader();
 
 #if SK_SUPPORT_GPU
@@ -63,8 +63,8 @@ public:
     };
 
 #ifdef SK_DEBUG
-    SkShader* getShaderA() { return fShaderA; }
-    SkShader* getShaderB() { return fShaderB; }
+    SkShader* getShaderA() { return fShaderA.get(); }
+    SkShader* getShaderB() { return fShaderB.get(); }
 #endif
 
     bool asACompose(ComposeRec* rec) const override;
@@ -79,9 +79,9 @@ protected:
     Context* onCreateContext(const ContextRec&, void*) const override;
 
 private:
-    SkShader*   fShaderA;
-    SkShader*   fShaderB;
-    SkXfermode* fMode;
+    sk_sp<SkShader> fShaderA;
+    sk_sp<SkShader> fShaderB;
+    SkXfermode*     fMode;
 
     typedef SkShader INHERITED;
 };