Replace fWillReadFragmentPosition with a bitfield

src/gpu/batches/GrPLSPathRenderer.cpp

Index: src/gpu/batches/GrPLSPathRenderer.cpp
diff --git a/src/gpu/batches/GrPLSPathRenderer.cpp b/src/gpu/batches/GrPLSPathRenderer.cpp
index c94eb07aa1866f4f3209410c02811371672e3247..69cfcd382e0da55aaaae78952cbde01ed7b60f0c 100644
--- a/src/gpu/batches/GrPLSPathRenderer.cpp
+++ b/src/gpu/batches/GrPLSPathRenderer.cpp
@@ -430,7 +430,7 @@ private:
                                                       kHigh_GrSLPrecision));
         fInWindings = &this->addVertexAttrib(Attribute("inWindings", kInt_GrVertexAttribType, 
                                                        kLow_GrSLPrecision));
-        this->setWillReadFragmentPosition();
+        this->enableBuiltInState(kFragmentPosition_BuiltInState);
     }
 
     const Attribute* fInPosition;
@@ -619,7 +619,7 @@ private:
                                                         kHigh_GrSLPrecision));
         fInWindings  = &this->addVertexAttrib(Attribute("inWindings", kInt_GrVertexAttribType, 
                                                         kLow_GrSLPrecision));
-        this->setWillReadFragmentPosition();
+        this->enableBuiltInState(kFragmentPosition_BuiltInState);
     }
 
     const Attribute* fInPosition;