Initial change to create GeometryProcessor

BUG=skia:
R=bsalomon@google.com, robertphillips@google.com, egdaniel@google.com, jvanverth@google.com

Author: joshualitt@chromium.org

Review URL: https://codereview.chromium.org/509153002
diff --git a/src/gpu/effects/GrDashingEffect.cpp b/src/gpu/effects/GrDashingEffect.cpp
index adee4ae..f4298eb 100644
--- a/src/gpu/effects/GrDashingEffect.cpp
+++ b/src/gpu/effects/GrDashingEffect.cpp
@@ -345,7 +345,7 @@
         bool isRoundCap = SkPaint::kRound_Cap == cap;
         GrDashingEffect::DashCap capType = isRoundCap ? GrDashingEffect::kRound_DashCap :
                                                         GrDashingEffect::kNonRound_DashCap;
-        drawState->addCoverageEffect(
+        drawState->setGeometryProcessor(
             GrDashingEffect::Create(edgeType, devInfo, strokeWidth, capType), 1)->unref();
     }