implemented copy surface as draw then blit for metal gpu backend

Bug: skia:
Change-Id: Ifa2d7ced7c22f74c2829d11b24557dbe851e3473
Reviewed-on: https://skia-review.googlesource.com/142691
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 11eb322..eaced6f 100644
--- a/src/gpu/mtl/GrMtlCaps.h
+++ b/src/gpu/mtl/GrMtlCaps.h
@@ -54,6 +54,9 @@
     bool canCopyAsDraw(GrPixelConfig dstConfig, bool dstIsRenderable,
                        GrPixelConfig srcConfig, bool srcIsTextureable) const;
 
+    bool canCopyAsDrawThenBlit(GrPixelConfig dstConfig, GrPixelConfig srcConfig,
+                               bool srcIsTextureable) const;
+
     bool canCopySurface(const GrSurfaceProxy* dst, const GrSurfaceProxy* src,
                         const SkIRect& srcRect, const SkIPoint& dstPoint) const override;