Add kRenderTarget_GrSurfaceFlag to GrVkGpu::onWrapBackendRenderTarget

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4868

Change-Id: I7f169d050c47c074cf63ef9b63fb7df8efdaed62
Reviewed-on: https://skia-review.googlesource.com/4868
Commit-Queue: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index 43bcd74..674e8e4 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -802,7 +802,7 @@
 
     GrSurfaceDesc desc;
     desc.fConfig = wrapDesc.fConfig;
-    desc.fFlags = kCheckAllocation_GrSurfaceFlag;
+    desc.fFlags = kCheckAllocation_GrSurfaceFlag | kRenderTarget_GrSurfaceFlag;
     desc.fWidth = wrapDesc.fWidth;
     desc.fHeight = wrapDesc.fHeight;
     desc.fSampleCnt = SkTMin(wrapDesc.fSampleCnt, this->caps()->maxSampleCount());