arc-bridge: Enable ARC with a command-line flag

chrome/browser/chromeos/chrome_browser_main_chromeos.h

Index: chrome/browser/chromeos/chrome_browser_main_chromeos.h
diff --git a/chrome/browser/chromeos/chrome_browser_main_chromeos.h b/chrome/browser/chromeos/chrome_browser_main_chromeos.h
index 10b3a3b7e8df01971f84a6a0e269fd70d752eb5d..0b546411c6fa438dd9a006fbae8dd1c3085c4182 100644
--- a/chrome/browser/chromeos/chrome_browser_main_chromeos.h
+++ b/chrome/browser/chromeos/chrome_browser_main_chromeos.h
@@ -15,11 +15,9 @@ namespace session_manager {
 class SessionManager;
 }
 
-#if defined(ENABLE_ARC)
 namespace arc {
 class ArcBridgeService;
 }
-#endif
 
 namespace chromeos {
 
@@ -83,9 +81,7 @@ class ChromeBrowserMainPartsChromeos : public ChromeBrowserMainPartsLinux {
 
   scoped_refptr<chromeos::ExternalMetrics> external_metrics_;
 
-#if defined(ENABLE_ARC)
   scoped_ptr<arc::ArcBridgeService> arc_bridge_service_;
-#endif
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainPartsChromeos);
 };