Begin removing deprecated (and now, unused) ImageFilter code paths

This CL focuses on removing the Proxy objects but takes some other stuff with it.

BUG=skia:4965
TBR=reed@google.com

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1896383003

Review URL: https://codereview.chromium.org/1896383003
diff --git a/src/core/SkSpecialSurface.h b/src/core/SkSpecialSurface.h
index d24ee74..6ed8a77 100644
--- a/src/core/SkSpecialSurface.h
+++ b/src/core/SkSpecialSurface.h
@@ -53,23 +53,20 @@
     /**
      *  Use an existing (renderTarget-capable) GrTexture as the backing store.
      */
-    static sk_sp<SkSpecialSurface> MakeFromTexture(SkImageFilter::Proxy* proxy,
-                                                   const SkIRect& subset, GrTexture*,
+    static sk_sp<SkSpecialSurface> MakeFromTexture(const SkIRect& subset, GrTexture*,
                                                    const SkSurfaceProps* = nullptr);
 
     /**
      *  Allocate a new GPU-backed SkSpecialSurface. If the requested surface cannot
      *  be created, nullptr will be returned.
      */
-    static sk_sp<SkSpecialSurface> MakeRenderTarget(SkImageFilter::Proxy* proxy,
-                                                    GrContext*, const GrSurfaceDesc&,
+    static sk_sp<SkSpecialSurface> MakeRenderTarget(GrContext*, const GrSurfaceDesc&,
                                                     const SkSurfaceProps* = nullptr);
 
     /**
      * Use and existing SkBitmap as the backing store.
      */
-    static sk_sp<SkSpecialSurface> MakeFromBitmap(SkImageFilter::Proxy* proxy,
-                                                  const SkIRect& subset, SkBitmap& bm,
+    static sk_sp<SkSpecialSurface> MakeFromBitmap(const SkIRect& subset, SkBitmap& bm,
                                                   const SkSurfaceProps* = nullptr);
 
     /**
@@ -79,27 +76,20 @@
      *  If the requested surface cannot be created, or the request is not a
      *  supported configuration, nullptr will be returned.
      */
-    static sk_sp<SkSpecialSurface> MakeRaster(SkImageFilter::Proxy* proxy,
-                                              const SkImageInfo&,
+    static sk_sp<SkSpecialSurface> MakeRaster(const SkImageInfo&,
                                               const SkSurfaceProps* = nullptr);
 
 protected:
-    SkSpecialSurface(SkImageFilter::Proxy*, const SkIRect& subset, const SkSurfaceProps*);
+    SkSpecialSurface(const SkIRect& subset, const SkSurfaceProps*);
 
     // For testing only
     friend class TestingSpecialSurfaceAccess;
     const SkIRect& subset() const { return fSubset; }
 
-    // TODO: remove this ASAP (see skbug.com/4965)
-    SkImageFilter::Proxy* proxy() const { return fProxy; }
-
 private:
     const SkSurfaceProps fProps;
     const SkIRect        fSubset;
 
-    // TODO: remove this ASAP (see skbug.com/4965)
-    SkImageFilter::Proxy* fProxy;
-
     typedef SkRefCnt INHERITED;
 };