[sksg] Add 'plane' geometry node

SG geometry corresponding to SkCanvas::drawPaint().

TBR=

Change-Id: I3b368adda187fb92f524756496a3694c03a3113d
Reviewed-on: https://skia-review.googlesource.com/108562
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 1c1fe38..f50f7be 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1401,6 +1401,7 @@
       "experimental/sksg/geometry/SkSGGeometryTransform.cpp",
       "experimental/sksg/geometry/SkSGMerge.cpp",
       "experimental/sksg/geometry/SkSGPath.cpp",
+      "experimental/sksg/geometry/SkSGPlane.cpp",
       "experimental/sksg/geometry/SkSGRect.cpp",
       "experimental/sksg/geometry/SkSGText.cpp",
       "experimental/sksg/geometry/SkSGTrimEffect.cpp",