Add SkImage factory method that forces image to be resolved to a texture.

include/core/SkImage.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_DEFINED
 #define SkImage_DEFINED
 
@@ skipping 124 matching lines @@
     /**
      *  Create a new image by copying the pixels from the specified y, u, v textures. The data
      *  from the textures is immediately ingested into the image and the textures can be modified or
      *  deleted after the function returns. The image will have the dimensions of the y texture.
      */
     static SkImage* NewFromYUVTexturesCopy(GrContext*, SkYUVColorSpace,
                                            const GrBackendObject yuvTextureHandles[3],
                                            const SkISize yuvSizes[3],
                                            GrSurfaceOrigin);
 
+    /**
+     *  Ensures that an image is backed by a texture (when GrContext is non-null). If no
+     *  transformation is required, the returned image may be the same as the one passed in.
+     *  If the input image is from a different GrContext, this will fail.
+     */
+    static SkImage* NewTextureImageFromImage(GrContext*, SkImage*);

[reed1, 2016/01/29 17:19:10]

nit:

SkImage* newTextureImage(GrContext*) const;

ala newSubset()

+
     static SkImage* NewFromPicture(const SkPicture*, const SkISize& dimensions,
                                    const SkMatrix*, const SkPaint*);
 
     ///////////////////////////////////////////////////////////////////////////////////////////////
 
     int width() const { return fWidth; }
     int height() const { return fHeight; }
     SkISize dimensions() const { return SkISize::Make(fWidth, fHeight); }
     SkIRect bounds() const { return SkIRect::MakeWH(fWidth, fHeight); }
     uint32_t uniqueID() const { return fUniqueID; }
@@ skipping 174 matching lines @@
 
 private:
     const int       fWidth;
     const int       fHeight;
     const uint32_t  fUniqueID;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif