Add a src rect to drawImageLattice() API

This will allow us to draw ninepatches directly from an asset
texture without having to upload them individually.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2382893002

Review-Url: https://codereview.chromium.org/2382893002
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index a50b5c6..d4d361d 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -1501,7 +1501,7 @@
     }
 
     std::unique_ptr<SkLatticeIter> iter(
-            new SkLatticeIter(producer->width(), producer->height(), lattice, dst));
+            new SkLatticeIter(lattice, dst));
     fDrawContext->drawImageLattice(fClip, grPaint, *draw.fMatrix, producer->width(),
                                    producer->height(), std::move(iter), dst);
 }