Create helper functions to use in computeInvariantOutput calls

src/effects/SkBlurMaskFilter.cpp

Index: src/effects/SkBlurMaskFilter.cpp
diff --git a/src/effects/SkBlurMaskFilter.cpp b/src/effects/SkBlurMaskFilter.cpp
index 79cf7e64949f21346990ba07560ba74961308029..42ce9b5aa90878d3ade25305d98133e552460670 100644
--- a/src/effects/SkBlurMaskFilter.cpp
+++ b/src/effects/SkBlurMaskFilter.cpp
@@ -766,8 +766,7 @@ bool GrRectBlurEffect::onIsEqual(const GrProcessor& sBase) const {
 }
 
 void GrRectBlurEffect::onComputeInvariantOutput(InvariantOutput* inout) const {
-    inout->fValidFlags = 0;
-    inout->fIsSingleComponent = false;
+    inout->unknownOutput();

[bsalomon, 2014/10/10 19:48:16]

I think this can be mulByUnknownAlpha()

[egdaniel, 2014/10/13 16:44:57]

Done.

 }
 
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrRectBlurEffect);
@@ -930,8 +929,7 @@ GrFragmentProcessor* GrRRectBlurEffect::Create(GrContext* context, float sigma,
 }
 
 void GrRRectBlurEffect::onComputeInvariantOutput(InvariantOutput* inout) const {
-    inout->fValidFlags = 0;
-    inout->fIsSingleComponent = false;
+    inout->unknownOutput();

[bsalomon, 2014/10/10 19:48:16]

and this

[egdaniel, 2014/10/13 16:44:57]

Done.

 }
 
 const GrBackendFragmentProcessorFactory& GrRRectBlurEffect::getFactory() const {