[Sync] Allow sync start without sign-in if the local sync backend is on.

components/browser_sync/profile_sync_service.cc

Index: components/browser_sync/profile_sync_service.cc
diff --git a/components/browser_sync/profile_sync_service.cc b/components/browser_sync/profile_sync_service.cc
index b4a269f8b8beee2d043b5ec65da26393b5aa3480..d82f173f591f58726f092503ce2ee90093983ce0 100644
--- a/components/browser_sync/profile_sync_service.cc
+++ b/components/browser_sync/profile_sync_service.cc
@@ -20,7 +20,6 @@
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/metrics/histogram.h"
-#include "base/path_service.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
@@ -152,11 +151,6 @@ static const base::FilePath::CharType kSyncDataFolderName[] =
 static const base::FilePath::CharType kLevelDBFolderName[] =
     FILE_PATH_LITERAL("LevelDB");
 
-#if defined(OS_WIN)
-static const base::FilePath::CharType kLoopbackServerBackendFilename[] =
-    FILE_PATH_LITERAL("profile.pb");
-#endif
-
 namespace {
 
 // Perform the actual sync data folder deletion.
@@ -184,7 +178,8 @@ ProfileSyncService::InitParams::InitParams(InitParams&& other)  // NOLINT
       url_request_context(std::move(other.url_request_context)),
       debug_identifier(std::move(other.debug_identifier)),
       channel(other.channel),
-      blocking_pool(other.blocking_pool) {}
+      blocking_pool(other.blocking_pool),
+      local_sync_backend_folder(other.local_sync_backend_folder) {}
 
 ProfileSyncService::ProfileSyncService(InitParams init_params)
     : OAuth2TokenService::Consumer("sync"),
@@ -206,6 +201,7 @@ ProfileSyncService::ProfileSyncService(InitParams init_params)
       engine_initialized_(false),
       sync_disabled_by_admin_(false),
       is_auth_in_progress_(false),
+      local_sync_backend_folder_(init_params.local_sync_backend_folder),
       signin_(std::move(init_params.signin_wrapper)),
       unrecoverable_error_reason_(ERROR_REASON_UNSET),
       expect_sync_configuration_aborted_(false),
@@ -252,7 +248,8 @@ ProfileSyncService::~ProfileSyncService() {
 
 bool ProfileSyncService::CanSyncStart() const {
   DCHECK(thread_checker_.CalledOnValidThread());
-  return IsSyncAllowed() && IsSyncRequested() && IsSignedIn();
+  return (IsSyncAllowed() && IsSyncRequested() &&
+          (IsLocalSyncEnabled() || IsSignedIn()));
 }
 
 void ProfileSyncService::Initialize() {
@@ -319,7 +316,7 @@ void ProfileSyncService::Initialize() {
   sync_prefs_.AddSyncPrefObserver(this);
 
   SyncInitialState sync_state = CAN_START;
-  if (!IsSignedIn()) {
+  if (!IsLocalSyncEnabled() && !IsSignedIn()) {
     sync_state = NOT_SIGNED_IN;
   } else if (IsManaged()) {
     sync_state = IS_MANAGED;
@@ -346,11 +343,13 @@ void ProfileSyncService::Initialize() {
     return;
   }
 
-  RegisterAuthNotifications();
+  if (!IsLocalSyncEnabled()) {
+    RegisterAuthNotifications();
 
-  if (!IsSignedIn()) {
-    // Clean up in case of previous crash during signout.
-    StopImpl(CLEAR_DATA);
+    if (!IsSignedIn()) {
+      // Clean up in case of previous crash during signout.
+      StopImpl(CLEAR_DATA);
+    }
   }
 
 #if defined(OS_CHROMEOS)
@@ -373,8 +372,8 @@ void ProfileSyncService::Initialize() {
                  sync_enabled_weak_factory_.GetWeakPtr()));
   startup_controller_->Reset(GetRegisteredDataTypes());
 
-  // Auto-start means means the first time the profile starts up, sync should
-  // start up immediately.
+  // Auto-start means the first time the profile starts up, sync should start up
+  // immediately.
   if (start_behavior_ == AUTO_START && IsSyncRequested() &&
       !IsFirstSetupComplete()) {
     startup_controller_->TryStartImmediately();
@@ -406,7 +405,8 @@ void ProfileSyncService::UnregisterAuthNotifications() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (signin())
     signin()->RemoveObserver(this);
-  oauth2_token_service_->RemoveObserver(this);
+  if (oauth2_token_service_)
+    oauth2_token_service_->RemoveObserver(this);
 }
 
 void ProfileSyncService::RegisterDataTypeController(
@@ -482,6 +482,11 @@ void ProfileSyncService::OnSessionRestoreComplete() {
 
 SyncCredentials ProfileSyncService::GetCredentials() {
   SyncCredentials credentials;
+
+  // No credentials exist or are needed for the local sync backend.
+  if (IsLocalSyncEnabled())
+    return credentials;
+
   credentials.account_id = signin_->GetAccountIdToUse();
   DCHECK(!credentials.account_id.empty());
   credentials.email = signin_->GetEffectiveUsername();
@@ -517,31 +522,6 @@ void ProfileSyncService::InitializeEngine(bool delete_stale_data) {
   if (delete_stale_data)
     ClearStaleErrors();
 
-  bool enable_local_sync_backend = false;
-  base::FilePath local_sync_backend_folder =
-      sync_prefs_.GetLocalSyncBackendDir();
-#if defined(OS_WIN)
-  enable_local_sync_backend = sync_prefs_.IsLocalSyncEnabled();
-  if (local_sync_backend_folder.empty()) {
-    // TODO(pastarmovj): Add DIR_ROAMING_USER_DATA to PathService to simplify
-    // this code and move the logic in its right place. See crbug/657810.
-    CHECK(
-        base::PathService::Get(base::DIR_APP_DATA, &local_sync_backend_folder));
-    local_sync_backend_folder =
-        local_sync_backend_folder.Append(FILE_PATH_LITERAL("Chrome/User Data"));
-  }
-  // This code as it is now will assume the same profile order is present on all
-  // machines, which is not a given. It is to be defined if only the Default
-  // profile should get this treatment or all profile as is the case now. The
-  // solution for now will be to assume profiles are created in the same order
-  // on all machines and in the future decide if only the Default one should be
-  // considered roamed.
-  local_sync_backend_folder =
-      local_sync_backend_folder.Append(base_directory_.BaseName());
-  local_sync_backend_folder =
-      local_sync_backend_folder.Append(kLoopbackServerBackendFilename);
-#endif  // defined(OS_WIN)
-
   SyncEngine::HttpPostProviderFactoryGetter http_post_provider_factory_getter =
       base::Bind(&syncer::NetworkResources::GetHttpPostProviderFactory,
                  base::Unretained(network_resources_.get()),
@@ -550,7 +530,7 @@ void ProfileSyncService::InitializeEngine(bool delete_stale_data) {
   engine_->Initialize(
       this, sync_thread_->task_runner(), GetJsEventHandler(), sync_service_url_,
       local_device_->GetSyncUserAgent(), credentials, delete_stale_data,
-      enable_local_sync_backend, local_sync_backend_folder,
+      IsLocalSyncEnabled(), local_sync_backend_folder_,
       base::MakeUnique<syncer::SyncManagerFactory>(),
       MakeWeakHandle(sync_enabled_weak_factory_.GetWeakPtr()),
       base::Bind(syncer::ReportUnrecoverableError, channel_),
@@ -997,10 +977,15 @@ void ProfileSyncService::OnEngineInitialized(
   sync_js_controller_.AttachJsBackend(js_backend);
   debug_info_listener_ = debug_info_listener;
 
-  SigninClient* signin_client = signin_->GetOriginal()->signin_client();
-  DCHECK(signin_client);
-  std::string signin_scoped_device_id =
-      signin_client->GetSigninScopedDeviceId();
+  std::string signin_scoped_device_id;
+  if (IsLocalSyncEnabled()) {
+    signin_scoped_device_id = "local_device";
+  } else {
+    SigninClient* signin_client = signin_->GetOriginal()->signin_client();
+    DCHECK(signin_client);
+    std::string signin_scoped_device_id =
+        signin_client->GetSigninScopedDeviceId();
+  }
 
   // Initialize local device info.
   local_device_->Initialize(cache_guid, signin_scoped_device_id,
@@ -1050,6 +1035,10 @@ void ProfileSyncService::OnEngineInitialized(
   }
 
   NotifyObservers();
+
+  // Nobody will call us to start if no sign in is going to happen.
+  if (IsLocalSyncEnabled())
+    RequestStart();
 }
 
 void ProfileSyncService::OnSyncCycleCompleted() {
@@ -1565,6 +1554,11 @@ bool ProfileSyncService::IsSyncActive() const {
          data_type_manager_->state() != DataTypeManager::STOPPED;
 }
 
+bool ProfileSyncService::IsLocalSyncEnabled() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return sync_prefs_.IsLocalSyncEnabled();
+}
+
 void ProfileSyncService::TriggerRefresh(const syncer::ModelTypeSet& types) {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (engine_initialized_)
@@ -1577,6 +1571,8 @@ bool ProfileSyncService::IsSignedIn() const {
 }
 
 bool ProfileSyncService::CanEngineStart() const {
+  if (IsLocalSyncEnabled())
+    return true;
   return CanSyncStart() && oauth2_token_service_ &&
          oauth2_token_service_->RefreshTokenIsAvailable(
              signin_->GetAccountIdToUse());
@@ -2534,7 +2530,7 @@ bool ProfileSyncService::HasSyncingEngine() const {
 }
 
 void ProfileSyncService::UpdateFirstSyncTimePref() {
-  if (!IsSignedIn()) {
+  if (!IsLocalSyncEnabled() && !IsSignedIn()) {
     sync_prefs_.ClearFirstSyncTime();
   } else if (sync_prefs_.GetFirstSyncTime().is_null()) {
     // Set if not set before and it's syncing now.