move compose-shader into base-class as factory

src/core/SkComposeShader.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkComposeShader.h"
@@ skipping 234 matching lines @@
     if (fMode) {
         str->append(" Xfermode: ");
         fMode->toString(str);
     }
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+SkShader* SkShader::CreateComposeShader(SkShader* dst, SkShader* src, SkXfermode* xfer) {
+    if (!dst || !src) {
+        return nullptr;
+    }
+    return new SkComposeShader(dst, src, xfer);
+}
+
+SkShader* SkShader::CreateComposeShader(SkShader* dst, SkShader* src, SkXfermode::Mode mode) {
+    SkAutoTUnref<SkXfermode> xfer(SkXfermode::Create(mode));
+    return CreateComposeShader(dst, src, xfer);
+}