Revert of Fix LCD coverage regression in GrPorterDuffXPFactory

src/gpu/effects/GrPorterDuffXferProcessor.cpp

Index: src/gpu/effects/GrPorterDuffXferProcessor.cpp
diff --git a/src/gpu/effects/GrPorterDuffXferProcessor.cpp b/src/gpu/effects/GrPorterDuffXferProcessor.cpp
index bc61f499e42ba3263af5f57d7f4ed817f3ef7d7e..de0143aceaf72346f818ddce9b71278a5e812aef 100644
--- a/src/gpu/effects/GrPorterDuffXferProcessor.cpp
+++ b/src/gpu/effects/GrPorterDuffXferProcessor.cpp
@@ -744,16 +744,11 @@
 void GrPorterDuffXPFactory::getInvariantOutput(const GrProcOptInfo& colorPOI,
                                                const GrProcOptInfo& coveragePOI,
                                                GrXPFactory::InvariantOutput* output) const {
-    output->fWillBlendWithDst = true;
-    output->fBlendedColorFlags = kNone_GrColorComponentFlags;
-
-    // The LCD coverage XP doesn't use the blend table, and has no invariant output.
-    if (coveragePOI.isFourChannelOutput()) {
-        return;
-    }
-
     const BlendFormula& blendFormula = get_blend_formula(fXfermode, colorPOI, coveragePOI);
+
     if (blendFormula.usesDstColor()) {
+        output->fWillBlendWithDst = true;
+        output->fBlendedColorFlags = kNone_GrColorComponentFlags;
         return;
     }
 
@@ -773,18 +768,16 @@
             output->fBlendedColorFlags = colorPOI.validFlags();
             return;
 
-        default: return;
+        // TODO: update if we ever use const color.
+        default:
+            output->fBlendedColorFlags = kNone_GrColorComponentFlags;
+            return;
     }
 }
 
 bool GrPorterDuffXPFactory::willReadDstColor(const GrCaps& caps,
                                              const GrProcOptInfo& colorPOI,
                                              const GrProcOptInfo& coveragePOI) const {
-    // The LCD coverage XP doesn't use the blend table, and never requires a dst read.
-    if (coveragePOI.isFourChannelOutput()) {
-        return false;
-    }
-
     // Some formulas use dual source blending, so we fall back if it is required but not supported.
     return !caps.shaderCaps()->dualSourceBlendingSupport() &&
            get_blend_formula(fXfermode, colorPOI, coveragePOI).hasSecondaryOutput();