[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 38500ff9c27cffe52130422acb03ef145575b585..d1d4f1f962c1d44f70f0cc63ff2bd7dbb8c0e3ad 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 +178,9 @@ 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_enabled(other.local_sync_backend_enabled),
+      local_sync_backend_folder(other.local_sync_backend_folder) {}
 
 ProfileSyncService::ProfileSyncService(InitParams init_params)
     : OAuth2TokenService::Consumer("sync"),
@@ -206,6 +202,8 @@ ProfileSyncService::ProfileSyncService(InitParams init_params)
       backend_initialized_(false),
       sync_disabled_by_admin_(false),
       is_auth_in_progress_(false),
+      local_sync_backend_enabled_(init_params.local_sync_backend_enabled),
+      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),
@@ -250,7 +248,8 @@ ProfileSyncService::~ProfileSyncService() {
 }
 
 bool ProfileSyncService::CanSyncStart() const {
-  return IsSyncAllowed() && IsSyncRequested() && IsSignedIn();
+  return (IsSyncAllowed() && IsSyncRequested() &&
+          (local_sync_backend_enabled_ || IsSignedIn()));

[Nicolas Zea, 2016/11/19 00:36:42]

It seems like IsSyncRequested/IsSignedIn/IsSyncAllowed should all return true if
the sync backend is enabled. I worry overriding CanSyncStart but not those will
lead to bugs.

[pastarmovj, 2016/11/22 12:38:08]

I don't think this is the case but I might be misunderstanding something in
which case please correct my reasoning below:

IsSyncRequested is checking whether the prefs::kSyncSuppressStart is not set. I
think this is independent of the sync backend used.

IsSignedIn is technically false in local sync therefore I only ever OR it with
the local sync state.

IsSyncAllowed checks if sync is not disabled e.g. by flag which I believe again
should be respected even in local sync mode. Right now it might seem
counter-intuitive that someone will add both the local sync enabled flag and
disable sync flag but remember that eventually the local sync mode will be
controlled by policy too.

Happy to change something if you believe the reasoning above is wrong or
misguided.

 }
 
 void ProfileSyncService::Initialize() {
@@ -316,7 +315,7 @@ void ProfileSyncService::Initialize() {
   sync_prefs_.AddSyncPrefObserver(this);
 
   SyncInitialState sync_state = CAN_START;
-  if (!IsSignedIn()) {
+  if (!local_sync_backend_enabled_ && !IsSignedIn()) {
     sync_state = NOT_SIGNED_IN;
   } else if (IsManaged()) {
     sync_state = IS_MANAGED;
@@ -343,11 +342,13 @@ void ProfileSyncService::Initialize() {
     return;
   }
 
-  RegisterAuthNotifications();
+  if (!local_sync_backend_enabled_) {
+    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)
@@ -370,8 +371,8 @@ 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();
@@ -403,7 +404,8 @@ void ProfileSyncService::RegisterAuthNotifications() {
 void ProfileSyncService::UnregisterAuthNotifications() {
   if (signin())
     signin()->RemoveObserver(this);
-  oauth2_token_service_->RemoveObserver(this);
+  if (oauth2_token_service_)
+    oauth2_token_service_->RemoveObserver(this);
 }
 
 void ProfileSyncService::RegisterDataTypeController(
@@ -471,6 +473,11 @@ void ProfileSyncService::OnSessionRestoreComplete() {
 
 SyncCredentials ProfileSyncService::GetCredentials() {
   SyncCredentials credentials;
+
+  // No credentials exist or are needed for the local sync backend.
+  if (local_sync_backend_enabled_)
+    return credentials;
+
   credentials.account_id = signin_->GetAccountIdToUse();
   DCHECK(!credentials.account_id.empty());
   credentials.email = signin_->GetEffectiveUsername();
@@ -506,36 +513,6 @@ void ProfileSyncService::InitializeBackend(bool delete_stale_data) {
   if (delete_stale_data)
     ClearStaleErrors();
 
-  bool enable_local_sync_backend = false;
-  base::FilePath local_sync_backend_folder;
-#if defined(OS_WIN)
-  enable_local_sync_backend = base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kEnableLocalSyncBackend);
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kLocalSyncBackendDir)) {
-    local_sync_backend_folder =
-        base::CommandLine::ForCurrentProcess()->GetSwitchValuePath(
-            switches::kLocalSyncBackendDir);
-  } else {
-    // 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)
-
   SyncBackendHost::HttpPostProviderFactoryGetter
       http_post_provider_factory_getter =
           base::Bind(&syncer::NetworkResources::GetHttpPostProviderFactory,
@@ -545,7 +522,7 @@ void ProfileSyncService::InitializeBackend(bool delete_stale_data) {
   backend_->Initialize(
       this, sync_thread_.get(), GetJsEventHandler(), sync_service_url_,
       local_device_->GetSyncUserAgent(), credentials, delete_stale_data,
-      enable_local_sync_backend, local_sync_backend_folder,
+      local_sync_backend_enabled_, local_sync_backend_folder_,
       base::MakeUnique<syncer::SyncManagerFactory>(),
       MakeWeakHandle(sync_enabled_weak_factory_.GetWeakPtr()),
       base::Bind(syncer::ReportUnrecoverableError, channel_),
@@ -991,6 +968,10 @@ void ProfileSyncService::PostBackendInitialization() {
   }
 
   NotifyObservers();
+
+  // Nobody will call us to start if no sign in is going to happen.
+  if (local_sync_backend_enabled_)
+    RequestStart();
 }
 
 void ProfileSyncService::OnBackendInitialized(
@@ -1024,10 +1005,15 @@ void ProfileSyncService::OnBackendInitialized(
   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 (local_sync_backend_enabled_) {
+    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,
@@ -1542,6 +1528,8 @@ bool ProfileSyncService::IsSignedIn() const {
 }
 
 bool ProfileSyncService::CanBackendStart() const {
+  if (local_sync_backend_enabled_)
+    return true;
   return CanSyncStart() && oauth2_token_service_ &&
          oauth2_token_service_->RefreshTokenIsAvailable(
              signin_->GetAccountIdToUse());
@@ -2437,7 +2425,7 @@ bool ProfileSyncService::HasSyncingBackend() const {
 }
 
 void ProfileSyncService::UpdateFirstSyncTimePref() {
-  if (!IsSignedIn()) {
+  if (!local_sync_backend_enabled_ && !IsSignedIn()) {
     sync_prefs_.ClearFirstSyncTime();
   } else if (sync_prefs_.GetFirstSyncTime().is_null()) {
     // Set if not set before and it's syncing now.