Add Geometry processor to srcAlphaWillBeOne check.

BUG=skia:

Review URL: https://codereview.chromium.org/681333002
diff --git a/src/gpu/GrDrawState.cpp b/src/gpu/GrDrawState.cpp
index e1fa6da..c4b8154 100644
--- a/src/gpu/GrDrawState.cpp
+++ b/src/gpu/GrDrawState.cpp
@@ -747,6 +747,10 @@
             inoutCoverage.fColor = this->getCoverageColor();
         }
 
+        if (this->hasGeometryProcessor()) {
+            fGeometryProcessor->computeInvariantOutput(&inoutCoverage);
+        }
+
         // Run through the coverage stages
         for (int s = 0; s < this->numCoverageStages(); ++s) {
             const GrProcessor* processor = this->getCoverageStage(s).getProcessor();