Fix bug in reads fragment position on gpu.

src/gpu/GrPipeline.cpp

Index: src/gpu/GrPipeline.cpp
diff --git a/src/gpu/GrPipeline.cpp b/src/gpu/GrPipeline.cpp
index aef528d096bbe258dbbb372405f4ebbf9f4a8c59..47074b9e5f0ef370d2dde329b7b0e486447d3837 100644
--- a/src/gpu/GrPipeline.cpp
+++ b/src/gpu/GrPipeline.cpp
@@ -193,7 +193,7 @@ void GrPipeline::adjustProgramFromOptimizations(const GrPipelineBuilder& pipelin
         (flags & GrXferProcessor::kOverrideColor_OptFlag)) {
         *firstColorProcessorIdx = pipelineBuilder.numColorFragmentProcessors();
     } else {
-        if (coveragePOI.readsFragPosition()) {
+        if (colorPOI.readsFragPosition()) {
             fReadsFragPosition = true;
         }
     }