6 files changed, 69 insertions, 0 deletions
diff --git a/chrome/browser/sync/internal_api/DEPS b/chrome/browser/sync/internal_api/DEPS
index 7b8b578..a393f32 100644
--- a/chrome/browser/sync/internal_api/DEPS
+++ b/chrome/browser/sync/internal_api/DEPS
@@ -7,6 +7,9 @@ include_rules = [
   "-chrome/browser/sync/api",
   "-chrome/browser/sync/glue",
 
+  # Some functionality depends on command-line swithces
+  "+chrome/common/chrome_switches.h",
+
   # unittests need this for mac osx keychain overriding
   "+chrome/browser/password_manager/encryptor.h",
 
diff --git a/chrome/browser/sync/internal_api/sync_manager.cc b/chrome/browser/sync/internal_api/sync_manager.cc
index b2924b3..3669e68 100644
--- a/chrome/browser/sync/internal_api/sync_manager.cc
+++ b/chrome/browser/sync/internal_api/sync_manager.cc
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "base/base64.h"
+#include "base/command_line.h"
 #include "base/json/json_writer.h"
 #include "base/string_number_conversions.h"
 #include "base/values.h"
@@ -44,6 +45,7 @@
 #include "chrome/browser/sync/syncable/syncable.h"
 #include "chrome/browser/sync/util/cryptographer.h"
 #include "chrome/browser/sync/weak_handle.h"
+#include "chrome/common/chrome_switches.h"
 #include "net/base/network_change_notifier.h"
 
 using std::string;
@@ -257,6 +259,10 @@ class SyncManager::SyncInternal
   // Called when the user disables or enables a sync type.
   void UpdateEnabledTypes();
 
+  // Conditionally sets the flag in the Nigori node which instructs other
+  // clients to start syncing tabs.
+  void MaybeSetSyncTabsInNigoriNode(const syncable::ModelTypeSet enabled_types);
+
   // Tell the sync engine to start the syncing process.
   void StartSyncingNormally();
 
@@ -678,6 +684,11 @@ void SyncManager::UpdateEnabledTypes() {
   data_->UpdateEnabledTypes();
 }
 
+void SyncManager::MaybeSetSyncTabsInNigoriNode(
+    const syncable::ModelTypeSet enabled_types) {
+  data_->MaybeSetSyncTabsInNigoriNode(enabled_types);
+}
+
 bool SyncManager::InitialSyncEndedForAllEnabledTypes() {
   return data_->InitialSyncEndedForAllEnabledTypes();
 }
@@ -965,6 +976,30 @@ void SyncManager::SyncInternal::UpdateEnabledTypes() {
     enabled_types.insert(it->first);
   }
   sync_notifier_->UpdateEnabledTypes(enabled_types);
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSyncSessionsForOtherClients)) {
+    MaybeSetSyncTabsInNigoriNode(enabled_types);
+  }
+}
+
+void SyncManager::SyncInternal::MaybeSetSyncTabsInNigoriNode(
+    const syncable::ModelTypeSet enabled_types) {
+  // The initialized_ check is to ensure that we don't CHECK in GetUserShare
+  // when this is called on start-up. It's ok to ignore that case, since
+  // presumably this would've run when the user originally enabled sessions.
+  if (initialized_ && enabled_types.count(syncable::SESSIONS) > 0) {
+    WriteTransaction trans(FROM_HERE, GetUserShare());
+    WriteNode node(&trans);
+    if (!node.InitByTagLookup(kNigoriTag)) {
+      NOTREACHED() << "Unable to set 'sync_tabs' bit because Nigori node not "
+                   << "found.";
+      return;
+    }
+
+    sync_pb::NigoriSpecifics specifics(node.GetNigoriSpecifics());
+    specifics.set_sync_tabs(true);
+    node.SetNigoriSpecifics(specifics);
+  }
 }
 
 void SyncManager::SyncInternal::RaiseAuthNeededEvent() {
diff --git a/chrome/browser/sync/internal_api/sync_manager.h b/chrome/browser/sync/internal_api/sync_manager.h
index 98eeaa4..3f1f627 100644
--- a/chrome/browser/sync/internal_api/sync_manager.h
+++ b/chrome/browser/sync/internal_api/sync_manager.h
@@ -434,6 +434,10 @@ class SyncManager {
   // Called when the user disables or enables a sync type.
   void UpdateEnabledTypes();
 
+  // Conditionally sets the flag in the Nigori node which instructs other
+  // clients to start syncing tabs.
+  void MaybeSetSyncTabsInNigoriNode(const syncable::ModelTypeSet enabled_types);
+
   // Put the syncer in normal mode ready to perform nudges and polls.
   void StartSyncingNormally();
 
diff --git a/chrome/browser/sync/internal_api/syncapi_unittest.cc b/chrome/browser/sync/internal_api/syncapi_unittest.cc
index 721e31f..4ee77b7 100644
--- a/chrome/browser/sync/internal_api/syncapi_unittest.cc
+++ b/chrome/browser/sync/internal_api/syncapi_unittest.cc
@@ -916,6 +916,28 @@ TEST_F(SyncManagerTest, UpdateEnabledTypes) {
   EXPECT_EQ(2, update_enabled_types_call_count_);
 }
 
+TEST_F(SyncManagerTest, DoNotSyncTabsInNigoriNode) {
+  syncable::ModelTypeSet encrypted_types;
+  encrypted_types.insert(syncable::TYPED_URLS);
+  sync_manager_.MaybeSetSyncTabsInNigoriNode(encrypted_types);
+
+  ReadTransaction trans(FROM_HERE, sync_manager_.GetUserShare());
+  ReadNode node(&trans);
+  ASSERT_TRUE(node.InitByIdLookup(GetIdForDataType(syncable::NIGORI)));
+  EXPECT_FALSE(node.GetNigoriSpecifics().sync_tabs());
+}
+
+TEST_F(SyncManagerTest, SyncTabsInNigoriNode) {
+  syncable::ModelTypeSet encrypted_types;
+  encrypted_types.insert(syncable::SESSIONS);
+  sync_manager_.MaybeSetSyncTabsInNigoriNode(encrypted_types);
+
+  ReadTransaction trans(FROM_HERE, sync_manager_.GetUserShare());
+  ReadNode node(&trans);
+  ASSERT_TRUE(node.InitByIdLookup(GetIdForDataType(syncable::NIGORI)));
+  EXPECT_TRUE(node.GetNigoriSpecifics().sync_tabs());
+}
+
 TEST_F(SyncManagerTest, ProcessJsMessage) {
   const JsArgList kNoArgs;
 
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index dfab776..63aa4f7 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -537,6 +537,10 @@ const char kEnableSyncSearchEngines[]       = "enable-sync-search-engines";
 // Enable syncing browser sessions.
 const char kEnableSyncSessions[]            = "enable-sync-sessions";
 
+// Enable syncing browser sessions for other synced clients.
+const char kEnableSyncSessionsForOtherClients[] =
+    "enable-sync-sessions-for-other-clients";
+
 // Enables context menu for selecting groups of tabs.
 const char kEnableTabGroupsContextMenu[]     = "enable-tab-groups-context-menu";
 
diff --git a/chrome/common/chrome_switches.h b/chrome/common/chrome_switches.h
index 72768bc..997aabe 100644
--- a/chrome/common/chrome_switches.h
+++ b/chrome/common/chrome_switches.h
@@ -155,6 +155,7 @@ extern const char kEnableSSLCachedInfo[];
 extern const char kEnableSyncOAuth[];
 extern const char kEnableSyncSearchEngines[];
 extern const char kEnableSyncSessions[];
+extern const char kEnableSyncSessionsForOtherClients[];
 extern const char kEnableSyncedBookmarksFolder[];
 extern const char kEnableTabGroupsContextMenu[];
 extern const char kEnableTcpFastOpen[];