Add choke point for modifying non-AA rect draws (e.g., applying clipping)

src/gpu/batches/GrMSAAPathRenderer.cpp

Index: src/gpu/batches/GrMSAAPathRenderer.cpp
diff --git a/src/gpu/batches/GrMSAAPathRenderer.cpp b/src/gpu/batches/GrMSAAPathRenderer.cpp
index f0137c6ce945f7c6d1baee5cd28600555cd5a121..48765843a5274f4e76b9b413971d996a9d361485 100644
--- a/src/gpu/batches/GrMSAAPathRenderer.cpp
+++ b/src/gpu/batches/GrMSAAPathRenderer.cpp
@@ -658,6 +658,7 @@ bool GrMSAAPathRenderer::internalDrawPath(GrDrawContext* drawContext,
                     GrRectBatchFactory::CreateNonAAFill(paint.getColor(), viewM, bounds, nullptr,
                                                         &localMatrix));
 
+            SkASSERT(GrPipelineBuilder::kBoth_DrawFace == drawFace[p]);
             GrPipelineBuilder pipelineBuilder(paint, drawContext->mustUseHWAA(paint));
             pipelineBuilder.setDrawFace(drawFace[p]);
             if (passes[p]) {