Convert ExtensionProtocolTestHandler to RepeatingCallback

The handler is meant to be called repeatedly so convert to
RepeatingCallback. The caller already uses BindRepeating.

Bug: 1152268
Change-Id: I62af30b2ce6fa0234a7efd5f2788c4e045c25a00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2605876Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840334}

extensions/browser/extension_protocols.h

@@ -29,8 +29,8 @@ class HttpResponseHeaders;
 namespace extensions {
 
 using ExtensionProtocolTestHandler =
-    base::Callback<void(base::FilePath* directory_path,
-                        base::FilePath* relative_path)>;
+    base::RepeatingCallback<void(base::FilePath* directory_path,
+                                 base::FilePath* relative_path)>;
 
 // Builds HTTP headers for an extension request. Hashes the time to avoid
 // exposing the exact user installation time of the extension.