Enable web-based sign in flow by default. Can use command line argument

chrome/browser/ui/webui/sync_setup_handler.h

Index: chrome/browser/ui/webui/sync_setup_handler.h
diff --git a/chrome/browser/ui/webui/sync_setup_handler.h b/chrome/browser/ui/webui/sync_setup_handler.h
index 7c0fe25015406f5e5be2c57eee5565f2fe891a18..822459f92239e11921b72546e47f3d86ab3e6d4a 100644
--- a/chrome/browser/ui/webui/sync_setup_handler.h
+++ b/chrome/browser/ui/webui/sync_setup_handler.h
@@ -83,6 +83,8 @@ class SyncSetupHandler : public options::OptionsPageUIHandler,
   FRIEND_TEST_ALL_PREFIXES(SyncSetupHandlerTest, UnsuccessfullySetPassphrase);
   FRIEND_TEST_ALL_PREFIXES(SyncSetupHandlerTest, SubmitAuthWithInvalidUsername);
 
+  bool is_configuring_sync() const { return configuring_sync_; }
+  bool have_signin_tracker() const { return signin_tracker_; }
 
   // Subclasses must implement this to show the setup UI that's appropriate
   // for the page this is contained in.
@@ -139,6 +141,10 @@ class SyncSetupHandler : public options::OptionsPageUIHandler,
   // error UI.
   void DisplayGaiaLogin(bool fatal_error);
 
+  // When web-flow is enabled, displays the Gaia login form in a new tab.
+  // This function is virtual so that tests can override.
+  virtual void DisplayGaiaLoginInNewTab();
+
   // Displays the GAIA login form with a custom error message (used for errors
   // like "email address already in use by another profile"). No message
   // displayed if |error_message| is empty. Displays fatal error UI if