[Extensions] Allow shared resources between tests via _test_resources

extensions/browser/extension_protocols.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_BROWSER_EXTENSION_PROTOCOLS_H_
 #define EXTENSIONS_BROWSER_EXTENSION_PROTOCOLS_H_
 
 #include <memory>
 #include <string>
 
+#include "base/callback.h"
 #include "net/url_request/url_request_job_factory.h"
 
 namespace base {
+class FilePath;
 class Time;
 }
 
 namespace net {
+class URLRequest;
+class URLRequestJob;
 class HttpResponseHeaders;
 }
 
 namespace extensions {
+class InfoMap;
 
-class InfoMap;
+using ExtensionProtocolTestHandler =
+    base::Callback<net::URLRequestJob*(net::URLRequest*,
+                                       net::NetworkDelegate*,
+                                       const base::FilePath&)>;
 
 // Builds HTTP headers for an extension request. Hashes the time to avoid
 // exposing the exact user installation time of the extension.
 net::HttpResponseHeaders* BuildHttpHeaders(
     const std::string& content_security_policy,
     bool send_cors_header,
     const base::Time& last_modified_time);
 
 // Creates the handlers for the chrome-extension:// scheme. Pass true for
 // |is_incognito| only for incognito profiles and not for Chrome OS guest mode
 // profiles.
 std::unique_ptr<net::URLRequestJobFactory::ProtocolHandler>
 CreateExtensionProtocolHandler(bool is_incognito, InfoMap* extension_info_map);
 
+// Allows tests to set a special handler for chrome-extension:// urls. Note
+// that this goes through all the normal security checks; it's essentially a
+// way to map extra resources to be included in extensions.
+void SetExtensionProtocolTestHandler(ExtensionProtocolTestHandler* handler);
+
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_PROTOCOLS_H_