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

src/gpu/GrDrawTarget.cpp

Index: src/gpu/GrDrawTarget.cpp
diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index 86e0c82f225f1a6cf32e54602cb50c3c2375af82..31c27cea36fa6a99ff1186e95c81dad4b9dc9741 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -426,15 +426,13 @@ void GrDrawTarget::clear(const SkIRect* rect,
             drawContext->discard();
         }
 
-        // TODO: flip this into real draw!
-        GrPipelineBuilder pipelineBuilder;
-        pipelineBuilder.setXPFactory(GrPorterDuffXPFactory::Make(SkXfermode::kSrc_Mode));
-
         SkRect scalarRect = SkRect::Make(*rect);
-        SkAutoTUnref<GrDrawBatch> batch(
-                GrRectBatchFactory::CreateNonAAFill(color, SkMatrix::I(), scalarRect,
-                                                    nullptr, nullptr));
-        this->drawBatch(pipelineBuilder, drawContext, GrNoClip(), batch);
+
+        GrPaint paint;
+        paint.setColor4f(GrColor4f::FromGrColor(color));
+        paint.setXPFactory(GrPorterDuffXPFactory::Make(SkXfermode::kSrc_Mode));
+
+        drawContext->drawRect(GrNoClip(), paint, SkMatrix::I(), scalarRect);
     } else {
         GrBatch* batch = new GrClearBatch(*rect, color, drawContext->accessRenderTarget());
         this->recordBatch(batch);