Make onPrepareDraws const

src/gpu/batches/GrDrawAtlasBatch.cpp

Index: src/gpu/batches/GrDrawAtlasBatch.cpp
diff --git a/src/gpu/batches/GrDrawAtlasBatch.cpp b/src/gpu/batches/GrDrawAtlasBatch.cpp
index 3ee8f88e89455aef111fb53ea86d82fffdea1523..dab5b4f7c20601483b9ff24e3f9b4aa1fb42a278 100644
--- a/src/gpu/batches/GrDrawAtlasBatch.cpp
+++ b/src/gpu/batches/GrDrawAtlasBatch.cpp
@@ -51,7 +51,7 @@ static const GrGeometryProcessor* set_vertex_attributes(bool hasColors,
     return GrDefaultGeoProcFactory::Create(gpColor, coverage, localCoords, viewMatrix);
 }
 
-void GrDrawAtlasBatch::onPrepareDraws(Target* target) {
+void GrDrawAtlasBatch::onPrepareDraws(Target* target) const {
     // Setup geometry processor
     SkAutoTUnref<const GrGeometryProcessor> gp(set_vertex_attributes(this->hasColors(),
                                                                      this->color(),