content::ResourceFetcher use OnceCallback and BindOnce

Use OnceCallback for the completion callback.

Bug: 752028
Change-Id: I7135cd13ffe0a2bc7b314abb30a2a143296278dd
Reviewed-on: https://chromium-review.googlesource.com/646993
Reviewed-by: Taiju Tsuiki <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Matt Menke <[email protected]>
Commit-Queue: Takashi Toyoshima <[email protected]>
Cr-Commit-Position: refs/heads/master@{#499576}
diff --git a/content/renderer/fetchers/resource_fetcher_impl.h b/content/renderer/fetchers/resource_fetcher_impl.h
index 74a8cef..c9002c3c 100644
--- a/content/renderer/fetchers/resource_fetcher_impl.h
+++ b/content/renderer/fetchers/resource_fetcher_impl.h
@@ -34,12 +34,12 @@
   void SetHeader(const std::string& header, const std::string& value) override;
   void Start(blink::WebLocalFrame* frame,
              blink::WebURLRequest::RequestContext request_context,
-             const Callback& callback) override;
+             Callback callback) override;
   void Start(blink::WebLocalFrame* frame,
              blink::WebURLRequest::RequestContext request_context,
              mojom::URLLoaderFactory* url_loader_factory,
              const net::NetworkTrafficAnnotationTag& annotation_tag,
-             const Callback& callback,
+             Callback callback,
              size_t maximum_download_size) override;
   void SetTimeout(const base::TimeDelta& timeout) override;