Image filters: fix filtering of transparent black in CFIF.

src/effects/SkColorFilterImageFilter.cpp

Index: src/effects/SkColorFilterImageFilter.cpp
diff --git a/src/effects/SkColorFilterImageFilter.cpp b/src/effects/SkColorFilterImageFilter.cpp
index 8d412cc2f5579967e9d304c443183f5b5855ae7b..63d5942f6a5ceacc07a15cb62d4cd3c3a40e5a19 100644
--- a/src/effects/SkColorFilterImageFilter.cpp
+++ b/src/effects/SkColorFilterImageFilter.cpp
@@ -98,7 +98,9 @@ sk_sp<SkSpecialImage> SkColorFilterImageFilter::onFilterImage(SkSpecialImage* so
     if (fColorFilter->affectsTransparentBlack()) {
         // The subsequent input->draw() call may not fill the entire canvas. For filters which
         // affect transparent black, ensure that the filter is applied everywhere.
+        paint.setColor(SK_ColorTRANSPARENT);
         canvas->drawPaint(paint);
+        paint.setColor(SK_ColorBLACK);
     } else {
         canvas->clear(0x0);
     }