Simplify adding attributes to GrGeometryProcessor

src/gpu/GrPrimitiveProcessor.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPrimitiveProcessor_DEFINED
 #define GrPrimitiveProcessor_DEFINED
 
@@ skipping 138 matching lines @@
 public:
     // Only the GrGeometryProcessor subclass actually has a geo shader or vertex attributes, but
     // we put these calls on the base class to prevent having to cast
     virtual bool willUseGeoShader() const = 0;
 
     struct Attribute {
         Attribute()
             : fName(nullptr)
             , fType(kFloat_GrVertexAttribType)
             , fOffset(0) {}
-        Attribute(const char* name, GrVertexAttribType type,
-                  GrSLPrecision precision = kDefault_GrSLPrecision)
+        Attribute(const char* name, GrVertexAttribType type, GrSLPrecision precision)
             : fName(name)
             , fType(type)
             , fOffset(SkAlign4(GrVertexAttribTypeSize(type)))
             , fPrecision(precision) {}
         const char* fName;
         GrVertexAttribType fType;
         size_t fOffset;
         GrSLPrecision fPrecision;
     };
 
@@ skipping 62 matching lines @@
     size_t fVertexStride;
 
 private:
     void notifyRefCntIsZero() const final {};
     virtual bool hasExplicitLocalCoords() const = 0;
 
     typedef GrProcessor INHERITED;
 };
 
 #endif