Make GrContextThreadSafeProxy not a GrContext_Base

Once this API is retracted, we can rename it to something more sane.
The code base has some `fContextInfo` ivars of this type, suggesting it
was previously named ContextInfo. It could be a ContextGroup or something else.

Bug: skia:10318
Change-Id: I3471e2172f46163f98a94780f0d7eb3431894cda
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293556
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Adlai Holler <adlai@google.com>
diff --git a/src/gpu/GrContextPriv.h b/src/gpu/GrContextPriv.h
index d97f7ad..c5d3f72 100644
--- a/src/gpu/GrContextPriv.h
+++ b/src/gpu/GrContextPriv.h
@@ -74,7 +74,7 @@
     /**
      * Create a GrContext without a resource cache
      */
-    static sk_sp<GrContext> MakeDDL(const sk_sp<GrContextThreadSafeProxy>&);
+    static sk_sp<GrContext> MakeDDL(sk_sp<GrContextThreadSafeProxy>);
 
     /**
      * Finalizes all pending reads and writes to the surfaces and also performs an MSAA resolves