Third small fragment from "Reduce dependence on GrSurface's origin field"

TBR=bsalomon@google.com
Change-Id: Ifae30beb333e9d668fa1378e332e8a4d063a371e
Reviewed-on: https://skia-review.googlesource.com/26348
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrClipStackClip.cpp b/src/gpu/GrClipStackClip.cpp
index 9a93687..3a31d0b 100644
--- a/src/gpu/GrClipStackClip.cpp
+++ b/src/gpu/GrClipStackClip.cpp
@@ -418,6 +418,7 @@
         return nullptr;
     }
 
+    SkASSERT(result->origin() == kBottomLeft_GrSurfaceOrigin);
     resourceProvider->assignUniqueKeyToProxy(key, result.get());
     // MDB TODO (caching): this has to play nice with the GrSurfaceProxy's caching
     add_invalidate_on_pop_message(*fStack, reducedClip.elementsGenID(), key);
@@ -489,6 +490,7 @@
 
     sk_sp<GrTextureProxy> result(helper.toTextureProxy(context, SkBackingFit::kApprox));
 
+    SkASSERT(result->origin() == kTopLeft_GrSurfaceOrigin);
     context->resourceProvider()->assignUniqueKeyToProxy(key, result.get());
     // MDB TODO (caching): this has to play nice with the GrSurfaceProxy's caching
     add_invalidate_on_pop_message(*fStack, reducedClip.elementsGenID(), key);