factories should return baseclass, allowing the impl to specialize

gm/filterfastbounds.cpp

 /*
  * Copyright 2014 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 "SkBlurImageFilter.h"
 #include "SkDropShadowImageFilter.h"
@@ skipping 95 matching lines @@
         SkAutoTUnref<SkImageFilter> rotMIF(
             SkImageFilter::CreateMatrixFilter(rot, kLow_SkFilterQuality, source));
 
         add_paint(rotMIF, paints);
     }
 
     {
         static const SkDropShadowImageFilter::ShadowMode kBoth =
                     SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode;
 
-        SkAutoTUnref<SkDropShadowImageFilter> dsif(
+        SkAutoTUnref<SkImageFilter> dsif(
             SkDropShadowImageFilter::Create(10.0f, 10.0f,
                                             3.0f, 3.0f,
                                             SK_ColorRED, kBoth,
                                             source, nullptr));
 
         add_paint(dsif, paints);
     }
 
     {
-        SkAutoTUnref<SkDropShadowImageFilter> dsif(
+        SkAutoTUnref<SkImageFilter> dsif(
             SkDropShadowImageFilter::Create(27.0f, 27.0f,
                                             3.0f, 3.0f,
                                             SK_ColorRED,
                                             SkDropShadowImageFilter::kDrawShadowOnly_ShadowMode,
                                             source, nullptr));
 
         add_paint(dsif, paints);
     }
 
     {
-        SkAutoTUnref<SkBlurImageFilter> bif(SkBlurImageFilter::Create(3, 3, source));
+        SkAutoTUnref<SkImageFilter> bif(SkBlurImageFilter::Create(3, 3, source));
 
         add_paint(bif, paints);
     }
 
     {
-        SkAutoTUnref<SkOffsetImageFilter> oif(SkOffsetImageFilter::Create(15, 15, source));
+        SkAutoTUnref<SkImageFilter> oif(SkOffsetImageFilter::Create(15, 15, source));
 
         add_paint(oif, paints);
     }
 }
 
 // This GM visualizes the fast bounds for various combinations of geometry
 // and image filter
 class ImageFilterFastBoundGM : public GM {
 public:
     ImageFilterFastBoundGM() {
@@ skipping 163 matching lines @@
     }
 
 private:
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM(return new ImageFilterFastBoundGM;)
 }