Correct accounting for wrapped resources

BUG=skia:2889

Review URL: https://codereview.chromium.org/720033004
diff --git a/src/gpu/GrGpuResourceCacheAccess.h b/src/gpu/GrGpuResourceCacheAccess.h
index 3c3786d0..7d20fff 100644
--- a/src/gpu/GrGpuResourceCacheAccess.h
+++ b/src/gpu/GrGpuResourceCacheAccess.h
@@ -54,6 +54,8 @@
         return NULL;
     }
 
+    bool isWrapped() const { return fResource->isWrapped(); }
+
     /**
      * Called by the cache to delete the resource under normal circumstances.
      */