Add move assignment operator to GrSurfaceProxyView.

Bug: skia:9556
Change-Id: I3928a3f3350b222bda429195dc7115b9303d9598
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/269199
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrSurfaceProxyView.h b/src/gpu/GrSurfaceProxyView.h
index 5e891a6..6fe016f 100644
--- a/src/gpu/GrSurfaceProxyView.h
+++ b/src/gpu/GrSurfaceProxyView.h
@@ -32,6 +32,7 @@
     operator bool() const { return SkToBool(fProxy.get()); }
 
     GrSurfaceProxyView& operator=(const GrSurfaceProxyView&) = default;
+    GrSurfaceProxyView& operator=(GrSurfaceProxyView&& view) = default;
 
     bool operator==(const GrSurfaceProxyView& view) const {
         return fProxy->uniqueID() == view.fProxy->uniqueID() &&