base: Remove non-const refs from the MRUCache implementation.

components/dom_distiller/core/distilled_content_store.h

Index: components/dom_distiller/core/distilled_content_store.h
diff --git a/components/dom_distiller/core/distilled_content_store.h b/components/dom_distiller/core/distilled_content_store.h
index 0063dd37166eb4b993277aaafaa0861c12f05d13..7fcd55b40a786d1ca484b9b2ab7042f641058b7f 100644
--- a/components/dom_distiller/core/distilled_content_store.h
+++ b/components/dom_distiller/core/distilled_content_store.h
@@ -63,7 +63,7 @@ class InMemoryContentStore : public DistilledContentStore {
    public:
     explicit CacheDeletor(InMemoryContentStore* store);
     ~CacheDeletor();
-    void operator()(const DistilledArticleProto& proto);
+    void operator()(DistilledArticleProto* proto);
 
    private:
     InMemoryContentStore* store_;