[DICE] Enable sync for an account that is already present in the token service.

chrome/browser/ui/webui/signin/signin_dice_internals_handler.cc

 // Copyright 2017 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 "chrome/browser/ui/webui/signin/signin_dice_internals_handler.h"
 
 #include "base/values.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/signin/account_tracker_service_factory.h"
+#include "chrome/browser/signin/profile_oauth2_token_service_factory.h"
+#include "chrome/browser/signin/signin_manager_factory.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/sync/one_click_signin_sync_starter.h"
 
 SigninDiceInternalsHandler::SigninDiceInternalsHandler(Profile* profile)
     : profile_(profile) {
   DCHECK(profile_);
   DCHECK(!profile_->IsOffTheRecord());
 }
 
 SigninDiceInternalsHandler::~SigninDiceInternalsHandler() {}
 
 void SigninDiceInternalsHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "enableSync", base::Bind(&SigninDiceInternalsHandler::HandleEnableSync,
                                base::Unretained(this)));
 }
 
 void SigninDiceInternalsHandler::HandleEnableSync(const base::ListValue* args) {
-  // TODO(msarda): Implement start syncing.
-  VLOG(1) << "[Dice] Start syncing";
+  if (SigninManagerFactory::GetForProfile(profile_)->IsAuthenticated()) {
+    VLOG(1) << "[Dice] Cannot enable sync as profile is already authenticated";
+    return;
+  }
+
+  AccountTrackerService* tracker =
+      AccountTrackerServiceFactory::GetForProfile(profile_);
+  ProfileOAuth2TokenService* token_service =
+      ProfileOAuth2TokenServiceFactory::GetForProfile(profile_);
+  std::vector<std::string> account_ids = token_service->GetAccounts();
+  if (account_ids.empty()) {
+    VLOG(1) << "[Dice] No accounts available in the token service";
+    return;
+  }
+
+  Browser* browser = chrome::FindLastActiveWithProfile(profile_);
+  DCHECK(browser);
+  std::string account_id = account_ids[0];
+  std::string gaia_id = tracker->GetAccountInfo(account_id).gaia;
+  std::string email = tracker->GetAccountInfo(account_id).email;
+  VLOG(1) << "[Dice] Start syncing with account " << email;
+
+  OneClickSigninSyncStarter::Callback callback;
+  new OneClickSigninSyncStarter(

[pastarmovj, 2017/07/05 13:56:21]

nit: Please add a comment above that this class is of the suicidal type :) It 
is quite scary seeing this new without anything before it.

[msarda, 2017/07/05 15:53:59]

Done.

+      profile_, browser, gaia_id, email, "" /* password */,
+      "" /* refresh_token */, OneClickSigninSyncStarter::CURRENT_PROFILE,
+      OneClickSigninSyncStarter::CONFIRM_SYNC_SETTINGS_FIRST,
+      web_ui()->GetWebContents(),
+      OneClickSigninSyncStarter::CONFIRM_AFTER_SIGNIN,
+      GURL("") /* current_url */, GURL("") /* continue_url */, callback);
 }