[chrome.displaySource] Avoid compiler warning.

extensions/renderer/api/display_source/display_source_session.cc

 // Copyright 2015 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.
 
 #include "extensions/renderer/api/display_source/display_source_session.h"
 
 #if defined(ENABLE_WIFI_DISPLAY)
 #include "extensions/renderer/api/display_source/wifi_display/wifi_display_session.h"
 #endif
 
@@ skipping 22 matching lines @@
 
   terminated_callback_ = terminated_callback;
   error_callback_ = error_callback;
 }
 
 std::unique_ptr<DisplaySourceSession>
 DisplaySourceSessionFactory::CreateSession(
     const DisplaySourceSessionParams& params) {
 #if defined(ENABLE_WIFI_DISPLAY)
   return std::unique_ptr<DisplaySourceSession>(new WiFiDisplaySession(params));
+#else
+  return nullptr;
 #endif
-  return nullptr;

[e_hakkinen, 2016/04/28 12:45:32]

Unreachable code.

 }
 
 }  // namespace extensions