Remove GP from drawstate, revision of invariant output for GP

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/c6bc58eded89b0c0a36b8e20e193c200f297a0da

Review URL: https://codereview.chromium.org/791743003
diff --git a/src/effects/SkBlurMaskFilter.cpp b/src/effects/SkBlurMaskFilter.cpp
index feb321a..7c0bbb8 100644
--- a/src/effects/SkBlurMaskFilter.cpp
+++ b/src/effects/SkBlurMaskFilter.cpp
@@ -817,7 +817,7 @@
 }
 
 void GrRectBlurEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
-    inout->mulByUnknownAlpha();
+    inout->mulByUnknownSingleComponent();
 }
 
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrRectBlurEffect);
@@ -979,7 +979,7 @@
 }
 
 void GrRRectBlurEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
-    inout->mulByUnknownAlpha();
+    inout->mulByUnknownSingleComponent();
 }
 
 GrRRectBlurEffect::GrRRectBlurEffect(float sigma, const SkRRect& rrect, GrTexture *ninePatchTexture)