Add SkSpecialImage::makeTextureImage entry point & update filterInput

src/core/SkSpecialImage.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 SkSpecialImage_DEFINED
 #define SkSpecialImage_DEFINED
 
 #include "SkNextID.h"
 #include "SkRefCnt.h"
 
 // remove this when internal_getProxy goes away (see skbug.com/4965)
 #include "SkImageFilter.h"
 
+#include "SkImageInfo.h" // for SkAlphaType
+
+class GrContext;
 class GrTexture;
 class SkBitmap;
 class SkCanvas;
 class SkImage;
 struct SkImageInfo;
 class SkPaint;
+class SkPixmap;
 class SkSpecialSurface;
 
 enum {
     kNeedNewImageUniqueID_SpecialImage = 0
 };
 
 /**
  * This is a restricted form of SkImage solely intended for internal use. It
  * differs from SkImage in that:
  *      - it can only be backed by raster or gpu (no generators)
@@ skipping 11 matching lines @@
 
     int width() const { return fSubset.width(); }
     int height() const { return fSubset.height(); }
     const SkIRect& subset() const { return fSubset; }
 
     uint32_t uniqueID() const { return fUniqueID; }
     virtual bool isOpaque() const { return false; }
     virtual size_t getSize() const = 0;
 
     /**
+     *  Ensures that a special image is backed by a texture (when GrContext is non-null). If no
+     *  transformation is required, the returned image may be the same as this special image.
+     *  If this special image is from a different GrContext, this will fail.
+     */
+    sk_sp<SkSpecialImage> makeTextureImage(SkImageFilter::Proxy*, GrContext*);
+
+    /**
      *  Draw this SpecialImage into the canvas.
      */
     void draw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) const;
 
     static sk_sp<SkSpecialImage> MakeFromImage(SkImageFilter::Proxy*,
                                                const SkIRect& subset,
                                                sk_sp<SkImage>);
     static sk_sp<SkSpecialImage> MakeFromRaster(SkImageFilter::Proxy*,
                                                 const SkIRect& subset,
                                                 const SkBitmap&);
@@ skipping 69 matching lines @@
     const uint32_t  fUniqueID;
 
     // TODO: remove this ASAP (see skbug.com/4965)
     SkImageFilter::Proxy* fProxy;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif