Remove declaration of SkTextureImageSetTexture, which does not exist

Bug: skia:
Change-Id: Ifb7edcae491ef48fbc69324d9dfb97a298104db9
Reviewed-on: https://skia-review.googlesource.com/15073
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/src/core/SkImagePriv.h b/src/core/SkImagePriv.h
index 921fdc8..2e80019 100644
--- a/src/core/SkImagePriv.h
+++ b/src/core/SkImagePriv.h
@@ -50,11 +50,6 @@
 // in which case the surface may need to perform a copy-on-write.
 extern const SkPixelRef* SkBitmapImageGetPixelRef(const SkImage* rasterImage);
 
-// Update the texture wrapped by an image created with NewTexture. This
-// is called when a surface and image share the same GrTexture and the
-// surface needs to perform a copy-on-write
-extern void SkTextureImageSetTexture(SkImage* image, GrTexture* texture);
-
 /**
  *  Will attempt to upload and lock the contents of the image as a texture, so that subsequent
  *  draws to a gpu-target will come from that texture (and not by looking at the original image