Simplify common case for recttorect

Change-Id: I70e295a677b8cac3d578e3cd57472c833af03877
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/354336
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/samplecode/SampleStrokePath.cpp b/samplecode/SampleStrokePath.cpp
index dace79a..a77a915 100644
--- a/samplecode/SampleStrokePath.cpp
+++ b/samplecode/SampleStrokePath.cpp
@@ -35,9 +35,7 @@
     paint.setStrokeJoin(SkPaint::kRound_Join);
     paint.setStyle(SkPaint::kStroke_Style);
 
-    SkMatrix matrix;
-    matrix.setRectToRect(srcR, dstR, SkMatrix::kCenter_ScaleToFit);
-    canvas->concat(matrix);
+    canvas->concat(SkMatrix::RectToRect(srcR, dstR, SkMatrix::kCenter_ScaleToFit));
 
     canvas->drawPath(path, paint);
 }