Change signature of SkSpecialImage::draw to take SkScalars

src/core/SkSpecialSurface.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file
  */
 
 #ifndef SkSpecialSurface_DEFINED
 #define SkSpecialSurface_DEFINED
 
@@ skipping 27 matching lines @@
     *  surface. 
     *
     *  The canvas will be invalid after 'newImageSnapshot' is called.
     */
     SkCanvas* getCanvas();
 
     /**
     *  Returns an image of the current state of the surface pixels up to this
     *  point. The canvas returned by 'getCanvas' becomes invalidated by this
     *  call and no more drawing to this surface is allowed.
+    *
+    *  Note: the caller inherits a ref from this call that must be balanced
     */
     SkSpecialImage* newImageSnapshot();
 
     /**
      *  Use an existing (renderTarget-capable) GrTexture as the backing store.
      */
     static SkSpecialSurface* NewFromTexture(const SkIRect& subset, GrTexture*,
                                             const SkSurfaceProps* = nullptr);
 
     /**
@@ skipping 26 matching lines @@
     const SkIRect& subset() const { return fSubset; }
 
 private:
     const SkSurfaceProps fProps;
     const SkIRect        fSubset;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif