add gpu impl for shadermaskfilter

adds MulChildAlphaByInput
renames MulOutputByInputAlpha --> MulChildByInputAlpha

Bug: skia:7500
Change-Id: Ic0615d4d23a887fbee510901ed77a36f98a1b11d
Reviewed-on: https://skia-review.googlesource.com/102440
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/src/gpu/GrFragmentProcessor.h b/src/gpu/GrFragmentProcessor.h
index 4ec92627ad..fa674d5d80 100644
--- a/src/gpu/GrFragmentProcessor.h
+++ b/src/gpu/GrFragmentProcessor.h
@@ -33,8 +33,17 @@ public:
     *  does so by returning a parent FP that multiplies the passed in FPs output by the parent's
     *  input alpha. The passed in FP will not receive an input color.
     */
-    static std::unique_ptr<GrFragmentProcessor> MulOutputByInputAlpha(
-            std::unique_ptr<GrFragmentProcessor>);
+    static std::unique_ptr<GrFragmentProcessor> MulChildByInputAlpha(
+            std::unique_ptr<GrFragmentProcessor> child);
+
+    /**
+     *  Like MulChildByInputAlpha(), but reverses the sense of src and dst. In this case, return
+     *  the input modulated by the child's alpha. The passed in FP will not receive an input color.
+     *
+     *  output = input * child.a
+     */
+    static std::unique_ptr<GrFragmentProcessor> MulInputByChildAlpha(
+            std::unique_ptr<GrFragmentProcessor> child);
 
     /**
      *  This assumes that the input color to the returned processor will be unpremul and that the