change SkImage_Gpu to handle all filters (w/ and w/o gpu support

gm/spritebitmap.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkCanvas.h"
 #include "SkBlurImageFilter.h"
@@ skipping 123 matching lines @@
     canvas->drawImage(image, x, y, nullptr);
 }
 
 typedef SkImageFilter* (*ImageFilterFactory)();
 
 // +[]{...} did not work on windows (VS)
 // (ImageFilterFactory)[]{...} did not work on linux (gcc)
 // hence this cast function
 template <typename T> ImageFilterFactory IFCCast(T arg) { return arg; }
 
+// We expect that applying the filter will keep us in the same domain (raster or gpu)
+static void check_same_domain(SkImage* a, SkImage* b) {
+    SkASSERT(a->isTextureBacked() == b->isTextureBacked());
+}
+
 /**
  *  Compare output of drawSprite and drawBitmap (esp. clipping and imagefilters)
  */
 class ApplyFilterGM : public skiagm::GM {
 public:
     ApplyFilterGM() {}
 
 protected:
     SkString onShortName() override {
         return SkString("apply-filter");
@@ skipping 19 matching lines @@
 
         const SkScalar spacer = image0->width() * 3.0f / 2;
 
         for (auto&& factory : factories) {
             SkAutoTUnref<SkImageFilter> filter(factory());
 
             SkIPoint offset1, offset2;
             SkAutoTUnref<SkImage> image1(image0->applyFilter(filter, &offset1, true));
             SkAutoTUnref<SkImage> image2(image0->applyFilter(filter, &offset2, false));
 
+            check_same_domain(image0, image1);
+            check_same_domain(image0, image2);
+
             canvas->save();
             canvas->translate(30, 30);
             show_image(canvas, image0, SkIPoint::Make(0, 0));   // original
             canvas->translate(spacer, 0);
             show_image(canvas, image1, offset1);                // snug
             canvas->translate(spacer, 0);
             show_image(canvas, image2, offset2);                // not snug
 
             // Try drawing the original w/ the filter, to see that it "draws" the same as
             // when we have manually applied the filter (above).
@@ skipping 15 matching lines @@
 
             canvas->translate(0, spacer);
         }
     }
 
 private:
     typedef GM INHERITED;
 };
 DEF_GM( return new ApplyFilterGM; )