Add SkCharacterization creation helper to GrContextThreadSafeProxy (take 2)

TBR=bsalomon@google.com
Change-Id: Id96d4fdbb6889065f10a4a7e0c22a03ad9aa5fef
Reviewed-on: https://skia-review.googlesource.com/107000
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/vk/GrVkCaps.h b/src/gpu/vk/GrVkCaps.h
index 3449dd2..b6c8beb 100644
--- a/src/gpu/vk/GrVkCaps.h
+++ b/src/gpu/vk/GrVkCaps.h
@@ -113,6 +113,9 @@
     bool validateBackendRenderTarget(const GrBackendRenderTarget&, SkColorType,
                                      GrPixelConfig*) const override;
 
+    bool getConfigFromBackendFormat(const GrBackendFormat&, SkColorType,
+                                    GrPixelConfig*) const override;
+
 private:
     enum VkVendor {
         kAMD_VkVendor = 4098,