Ref GrDirectContext in MakeBackendRenderTargetSurface
Ref GrDirectContext in MakeBackendRenderTargetSurface

Fixes crashes when running vkbert config where we tear down a Vulkan
GrDirectContext before deleting the backing store of a SkSurface
created via MakeBackendRenderTargetSurface.

Bug: skia:10843
Change-Id: I99ea2266ba14325d3aaac5ee59aa712688fb9329
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/327196
Reviewed-by: Greg Daniel <39df0a804564ccb6cf75f18db79653821f37c1c5@google.com>
Commit-Queue: Brian Salomon <61fabaaf0876044aeedfd8e351e485c028d69e7b@google.com>

google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia