implemented copy surface as draw for metal gpu backend

Bug: skia:
Change-Id: Ie61bd6ad9f288b8a025d44f887a0954101a7d710
Reviewed-on: https://skia-review.googlesource.com/142687
Commit-Queue: Timothy Liang <timliang@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/mtl/GrMtlCaps.h b/src/gpu/mtl/GrMtlCaps.h
index 5d6c82b..11eb322 100644
--- a/src/gpu/mtl/GrMtlCaps.h
+++ b/src/gpu/mtl/GrMtlCaps.h
@@ -51,6 +51,9 @@
                        const SkIRect& srcRect, const SkIPoint& dstPoint,
                        bool areDstSrcSameObj) const;
 
+    bool canCopyAsDraw(GrPixelConfig dstConfig, bool dstIsRenderable,
+                       GrPixelConfig srcConfig, bool srcIsTextureable) const;
+
     bool canCopySurface(const GrSurfaceProxy* dst, const GrSurfaceProxy* src,
                         const SkIRect& srcRect, const SkIPoint& dstPoint) const override;