factories should return baseclass, allowing the impl to specialize

tests/ImageFilterTest.cpp

Index: tests/ImageFilterTest.cpp
diff --git a/tests/ImageFilterTest.cpp b/tests/ImageFilterTest.cpp
index b1a017cc52c7b20c9400080c725a08aad81b9d24..f83d315c4d4511b62865edff2948451bcb77fb28 100644
--- a/tests/ImageFilterTest.cpp
+++ b/tests/ImageFilterTest.cpp
@@ -354,16 +354,11 @@ static SkBitmap make_gradient_circle(int width, int height) {
 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;
-    SkScalar five = SkIntToScalar(5);
+    const int width = 32, height = 32;
+    const 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;
@@ -422,9 +417,9 @@ DEF_TEST(ImageFilterDrawTiled, reporter) {
         SkIntToScalar( 1), SkIntToScalar(-7), SkIntToScalar( 1),
         SkIntToScalar( 1), SkIntToScalar( 1), SkIntToScalar( 1),
     };
-    SkISize kernelSize = SkISize::Make(3, 3);
-    SkScalar gain = SK_Scalar1, bias = 0;
-    SkScalar five = SkIntToScalar(5);
+    const SkISize kernelSize = SkISize::Make(3, 3);
+    const SkScalar gain = SK_Scalar1, bias = 0;
+    const SkScalar five = SkIntToScalar(5);
 
     SkAutoTUnref<SkImage> gradientImage(SkImage::NewFromBitmap(make_gradient_circle(64, 64)));
     SkAutoTUnref<SkImageFilter> gradientSource(SkImageSource::Create(gradientImage));
@@ -489,7 +484,7 @@ DEF_TEST(ImageFilterDrawTiled, reporter) {
     };
 
     SkBitmap untiledResult, tiledResult;
-    int width = 64, height = 64;
+    const int width = 64, height = 64;
     untiledResult.allocN32Pixels(width, height);
     tiledResult.allocN32Pixels(width, height);
     SkCanvas tiledCanvas(tiledResult);