factories should return baseclass, allowing the impl to specialize

tests/ImageFilterTest.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 "SkBitmap.h"
 #include "SkBitmapDevice.h"
 #include "SkBlurImageFilter.h"
@@ skipping 336 matching lines @@
     );
     SkPaint paint;
     paint.setShader(shader);
     canvas.drawCircle(x, y, radius, paint);
     return bitmap;
 }
 
 static void test_negative_blur_sigma(SkImageFilter::Proxy* proxy, skiatest::Reporter* reporter) {
     // Check that SkBlurImageFilter will accept a negative sigma, either in
     // the given arguments or after CTM application.
     int width = 32, height = 32;

[robertphillips, 2015/10/06 11:43:12]

I feel this variable should, at the very least, be const.

[reed1, 2015/10/06 16:59:24]

Done.

     SkScalar five = SkIntToScalar(5);
 
-    SkAutoTUnref<SkBlurImageFilter> positiveFilter(
-        SkBlurImageFilter::Create(five, five)
-    );
-
-    SkAutoTUnref<SkBlurImageFilter> negativeFilter(
-        SkBlurImageFilter::Create(-five, five)
-    );
+    SkAutoTUnref<SkImageFilter> positiveFilter(SkBlurImageFilter::Create(five, five));
+    SkAutoTUnref<SkImageFilter> negativeFilter(SkBlurImageFilter::Create(-five, five));
 
     SkBitmap gradient = make_gradient_circle(width, height);
     SkBitmap positiveResult1, negativeResult1;
     SkBitmap positiveResult2, negativeResult2;
     SkIPoint offset;
     SkImageFilter::Context ctx(SkMatrix::I(), SkIRect::MakeLargest(), nullptr);
     positiveFilter->filterImage(proxy, gradient, ctx, &positiveResult1, &offset);
     negativeFilter->filterImage(proxy, gradient, ctx, &negativeResult1, &offset);
     SkMatrix negativeScale;
     negativeScale.setScale(-SK_Scalar1, SK_Scalar1);
@@ skipping 932 matching lines @@
                                                          SkSurface::kNo_Budgeted,
                                                          SkImageInfo::MakeN32Premul(1, 1),
                                                          0,
                                                          &props,
                                                          SkGpuDevice::kUninit_InitContents));
     SkImageFilter::Proxy proxy(device);
 
     test_negative_blur_sigma(&proxy, reporter);
 }
 #endif