[Sync] Convert SyncSessionSnapshot to a copy-able class.

Previously it was an immutable struct that was passed around by making
dynamic allocations and passing pointers. We now just have a class with
only getters and no setters, but support for default copy and assign.

This cleans up some code and makes some future work easier to pass snapshots
around.

BUG=none
TEST=sync_unit_tests


Review URL: http://codereview.chromium.org/10197004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133747 0039d316-1c4b-4281-b951-d872f2087c98

13 files changed, 129 insertions, 151 deletions

diff --git a/chrome/browser/sync/backend_migrator.cc b/chrome/browser/sync/backend_migrator.cc
index 3894bbd..e8eb407 100644
--- a/chrome/browser/sync/backend_migrator.cc
+++ b/chrome/browser/sync/backend_migrator.cc
@@ -20,7 +20,6 @@ using syncable::ModelTypeSet;
 
 namespace browser_sync {
 
-using sessions::SyncSessionSnapshot;
 using syncable::ModelTypeToString;
 
 MigrationObserver::~MigrationObserver() {}
diff --git a/chrome/browser/sync/glue/sync_backend_host.cc b/chrome/browser/sync/glue/sync_backend_host.cc
index 0d59793..42aed59 100644
--- a/chrome/browser/sync/glue/sync_backend_host.cc
+++ b/chrome/browser/sync/glue/sync_backend_host.cc
@@ -45,7 +45,6 @@
 #include "sync/notifier/sync_notifier.h"
 #include "sync/protocol/encryption.pb.h"
 #include "sync/protocol/sync.pb.h"
-#include "sync/sessions/session_state.h"
 #include "sync/util/nigori.h"
 
 static const int kSaveChangesIntervalSeconds = 10;
@@ -81,7 +80,7 @@ class SyncBackendHost::Core
   // traffic controller here, forwarding incoming messages to appropriate
   // landing threads.
   virtual void OnSyncCycleCompleted(
-      const sessions::SyncSessionSnapshot* snapshot) OVERRIDE;
+      const sessions::SyncSessionSnapshot& snapshot) OVERRIDE;
   virtual void OnInitializationComplete(
       const WeakHandle<JsBackend>& js_backend,
       bool success) OVERRIDE;
@@ -614,8 +613,8 @@ SyncBackendHost::Status SyncBackendHost::GetDetailedStatus() {
   return core_->sync_manager()->GetDetailedStatus();
 }
 
-const SyncSessionSnapshot* SyncBackendHost::GetLastSessionSnapshot() const {
-  return last_snapshot_.get();
+SyncSessionSnapshot SyncBackendHost::GetLastSessionSnapshot() const {
+  return last_snapshot_;
 }
 
 bool SyncBackendHost::HasUnsyncedItems() const {
@@ -657,17 +656,17 @@ void SyncBackendHost::InitCore(const DoInitializeOptions& options) {
 }
 
 void SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop(
-    SyncSessionSnapshot* snapshot) {
+    const SyncSessionSnapshot& snapshot) {
   if (!frontend_)
     return;
   DCHECK_EQ(MessageLoop::current(), frontend_loop_);
 
-  last_snapshot_.reset(snapshot);
+  last_snapshot_ = snapshot;
 
-  SDVLOG(1) << "Got snapshot " << snapshot->ToString();
+  SDVLOG(1) << "Got snapshot " << snapshot.ToString();
 
   const syncable::ModelTypeSet to_migrate =
-      snapshot->syncer_status.types_needing_local_migration;
+      snapshot.syncer_status().types_needing_local_migration;
   if (!to_migrate.Empty())
     frontend_->OnMigrationNeededForTypes(to_migrate);
 
@@ -686,7 +685,7 @@ void SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop(
         pending_download_state_->added_types;
     DCHECK(types_to_add.HasAll(added_types));
     const syncable::ModelTypeSet initial_sync_ended =
-        snapshot->initial_sync_ended;
+        snapshot.initial_sync_ended();
     const syncable::ModelTypeSet failed_configuration_types =
         Difference(added_types, initial_sync_ended);
     SDVLOG(1)
@@ -698,7 +697,7 @@ void SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop(
         << syncable::ModelTypeSetToString(failed_configuration_types);
 
     if (!failed_configuration_types.Empty() &&
-        snapshot->retry_scheduled) {
+        snapshot.retry_scheduled()) {
       // Inform the caller that download failed but we are retrying.
       if (!pending_download_state_->retry_in_progress) {
         pending_download_state_->retry_callback.Run();
@@ -864,14 +863,14 @@ SyncBackendHost::PendingConfigureDataTypesState::
 ~PendingConfigureDataTypesState() {}
 
 void SyncBackendHost::Core::OnSyncCycleCompleted(
-    const SyncSessionSnapshot* snapshot) {
+    const SyncSessionSnapshot& snapshot) {
   if (!sync_loop_)
     return;
   DCHECK_EQ(MessageLoop::current(), sync_loop_);
   host_.Call(
       FROM_HERE,
       &SyncBackendHost::HandleSyncCycleCompletedOnFrontendLoop,
-      new SyncSessionSnapshot(*snapshot));
+      snapshot);
 }
 
 
diff --git a/chrome/browser/sync/glue/sync_backend_host.h b/chrome/browser/sync/glue/sync_backend_host.h
index 3073d6d..691586a 100644
--- a/chrome/browser/sync/glue/sync_backend_host.h
+++ b/chrome/browser/sync/glue/sync_backend_host.h
@@ -26,6 +26,7 @@
 #include "sync/notifier/sync_notifier_factory.h"
 #include "sync/protocol/encryption.pb.h"
 #include "sync/protocol/sync_protocol_error.h"
+#include "sync/sessions/session_state.h"
 #include "sync/syncable/model_type.h"
 #include "sync/util/report_unrecoverable_error_function.h"
 #include "sync/util/unrecoverable_error_handler.h"
@@ -36,10 +37,6 @@ class Profile;
 
 namespace browser_sync {
 
-namespace sessions {
-struct SyncSessionSnapshot;
-}
-
 class ChangeProcessor;
 class JsBackend;
 class JsEventHandler;
@@ -256,7 +253,7 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
   // Called from any thread to obtain current status information in detailed or
   // summarized form.
   Status GetDetailedStatus();
-  const sessions::SyncSessionSnapshot* GetLastSessionSnapshot() const;
+  sessions::SyncSessionSnapshot GetLastSessionSnapshot() const;
 
   // Determines if the underlying sync engine has made any local changes to
   // items that have not yet been synced with the server.
@@ -328,7 +325,7 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
   // Called from Core::OnSyncCycleCompleted to handle updating frontend
   // thread components.
   void HandleSyncCycleCompletedOnFrontendLoop(
-      sessions::SyncSessionSnapshot* snapshot);
+      const sessions::SyncSessionSnapshot& snapshot);
 
   // Called to finish the job of ConfigureDataTypes once the syncer is in
   // configuration mode.
@@ -515,7 +512,7 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
   sync_pb::EncryptedData cached_pending_keys_;
 
   // UI-thread cache of the last SyncSessionSnapshot received from syncapi.
-  scoped_ptr<sessions::SyncSessionSnapshot> last_snapshot_;
+  sessions::SyncSessionSnapshot last_snapshot_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
 };
diff --git a/chrome/browser/sync/profile_sync_service.cc b/chrome/browser/sync/profile_sync_service.cc
index 40910f0..5832936 100644
--- a/chrome/browser/sync/profile_sync_service.cc
+++ b/chrome/browser/sync/profile_sync_service.cc
@@ -1233,13 +1233,13 @@ sync_api::UserShare* ProfileSyncService::GetUserShare() const {
   return NULL;
 }
 
-const browser_sync::sessions::SyncSessionSnapshot*
+browser_sync::sessions::SyncSessionSnapshot
     ProfileSyncService::GetLastSessionSnapshot() const {
   if (backend_.get() && backend_initialized_) {
     return backend_->GetLastSessionSnapshot();
   }
   NOTREACHED();
-  return NULL;
+  return browser_sync::sessions::SyncSessionSnapshot();
 }
 
 bool ProfileSyncService::HasUnsyncedItems() const {
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index 0abf55d..3a779ba 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -48,7 +48,7 @@ class ChangeProcessor;
 class DataTypeManager;
 class JsController;
 class SessionModelAssociator;
-namespace sessions { struct SyncSessionSnapshot; }
+namespace sessions { class SyncSessionSnapshot; }
 }
 
 namespace sync_api {
@@ -360,7 +360,7 @@ class ProfileSyncService : public browser_sync::SyncFrontend,
   // ProfileSyncServiceHarness.  Figure out a different way to expose
   // this info to that class, and remove these functions.
 
-  virtual const browser_sync::sessions::SyncSessionSnapshot*
+  virtual browser_sync::sessions::SyncSessionSnapshot
       GetLastSessionSnapshot() const;
 
   // Returns whether or not the underlying sync engine has made any
diff --git a/chrome/browser/sync/profile_sync_service_harness.cc b/chrome/browser/sync/profile_sync_service_harness.cc
index d7bdb1c..d4073b6 100644
--- a/chrome/browser/sync/profile_sync_service_harness.cc
+++ b/chrome/browser/sync/profile_sync_service_harness.cc
@@ -337,7 +337,7 @@ bool ProfileSyncServiceHarness::RunStateChangeMachine() {
       // TODO(rlarocque): Figure out a less brittle way of detecting this.
       if (IsTypeEncrypted(waiting_for_encryption_type_) &&
           IsFullySynced() &&
-          GetLastSessionSnapshot()->num_encryption_conflicts == 0) {
+          GetLastSessionSnapshot().num_encryption_conflicts() == 0) {
         // Encryption is now complete for the the type in which we were waiting.
         SignalStateCompleteWithNextState(FULLY_SYNCED);
         break;
@@ -363,10 +363,8 @@ bool ProfileSyncServiceHarness::RunStateChangeMachine() {
     case WAITING_FOR_EXPONENTIAL_BACKOFF_VERIFICATION: {
       DVLOG(1) << GetClientInfoString(
           "WAITING_FOR_EXPONENTIAL_BACKOFF_VERIFICATION");
-      const browser_sync::sessions::SyncSessionSnapshot *snap =
-          GetLastSessionSnapshot();
-      CHECK(snap);
-      retry_verifier_.VerifyRetryInterval(*snap);
+      const SyncSessionSnapshot& snap = GetLastSessionSnapshot();
+      retry_verifier_.VerifyRetryInterval(snap);
       if (retry_verifier_.done()) {
         // Retry verifier is done verifying exponential backoff.
         SignalStateCompleteWithNextState(WAITING_FOR_NOTHING);
@@ -580,10 +578,8 @@ bool ProfileSyncServiceHarness::AwaitSyncDisabled(const std::string& reason) {
 }
 
 bool ProfileSyncServiceHarness::AwaitExponentialBackoffVerification() {
-  const browser_sync::sessions::SyncSessionSnapshot *snap =
-      GetLastSessionSnapshot();
-  CHECK(snap);
-  retry_verifier_.Initialize(*snap);
+  const SyncSessionSnapshot& snap = GetLastSessionSnapshot();
+  retry_verifier_.Initialize(snap);
   wait_state_ = WAITING_FOR_EXPONENTIAL_BACKOFF_VERIFICATION;
   AwaitStatusChangeWithTimeout(kExponentialBackoffVerificationTimeoutMs,
       "Verify Exponential backoff");
@@ -754,14 +750,13 @@ ProfileSyncService::Status ProfileSyncServiceHarness::GetStatus() {
 // We use this function to share code between IsFullySynced and IsDataSynced
 // while ensuring that all conditions are evaluated using on the same snapshot.
 bool ProfileSyncServiceHarness::IsDataSyncedImpl(
-    const browser_sync::sessions::SyncSessionSnapshot *snap) {
-  return snap &&
-      snap->num_simple_conflicts == 0 &&
-      ServiceIsPushingChanges() &&
-      GetStatus().notifications_enabled &&
-      !service()->HasUnsyncedItems() &&
-      !snap->has_more_to_sync &&
-      !HasPendingBackendMigration();
+    const SyncSessionSnapshot& snap) {
+  return snap.num_simple_conflicts() == 0 &&
+         ServiceIsPushingChanges() &&
+         GetStatus().notifications_enabled &&
+         !service()->HasUnsyncedItems() &&
+         !snap.has_more_to_sync() &&
+         !HasPendingBackendMigration();
 }
 
 bool ProfileSyncServiceHarness::IsDataSynced() {
@@ -770,7 +765,7 @@ bool ProfileSyncServiceHarness::IsDataSynced() {
     return false;
   }
 
-  const SyncSessionSnapshot* snap = GetLastSessionSnapshot();
+  const SyncSessionSnapshot& snap = GetLastSessionSnapshot();
   bool is_data_synced = IsDataSyncedImpl(snap);
 
   DVLOG(1) << GetClientInfoString(
@@ -783,11 +778,11 @@ bool ProfileSyncServiceHarness::IsFullySynced() {
     DVLOG(1) << GetClientInfoString("IsFullySynced: false");
     return false;
   }
-  const SyncSessionSnapshot* snap = GetLastSessionSnapshot();
-  // snap->unsynced_count == 0 is a fairly reliable indicator of whether or not
+  const SyncSessionSnapshot& snap = GetLastSessionSnapshot();
+  // snap.unsynced_count() == 0 is a fairly reliable indicator of whether or not
   // our timestamp is in sync with the server.
   bool is_fully_synced = IsDataSyncedImpl(snap) &&
-      snap->unsynced_count == 0;
+      snap.unsynced_count() == 0;
 
   DVLOG(1) << GetClientInfoString(
       is_fully_synced ? "IsFullySynced: true" : "IsFullySynced: false");
@@ -856,13 +851,12 @@ bool ProfileSyncServiceHarness::MatchesOtherClient(
   return true;
 }
 
-const SyncSessionSnapshot*
-    ProfileSyncServiceHarness::GetLastSessionSnapshot() const {
+SyncSessionSnapshot ProfileSyncServiceHarness::GetLastSessionSnapshot() const {
   DCHECK(service_ != NULL) << "Sync service has not yet been set up.";
   if (service_->sync_initialized()) {
     return service_->GetLastSessionSnapshot();
   }
-  return NULL;
+  return SyncSessionSnapshot();
 }
 
 bool ProfileSyncServiceHarness::EnableSyncForDatatype(
@@ -975,9 +969,8 @@ bool ProfileSyncServiceHarness::DisableSyncForAllDatatypes() {
 
 std::string ProfileSyncServiceHarness::GetUpdatedTimestamp(
     syncable::ModelType model_type) {
-  const SyncSessionSnapshot* snap = GetLastSessionSnapshot();
-  DCHECK(snap != NULL) << "GetUpdatedTimestamp(): Sync snapshot is NULL.";
-  return snap->download_progress_markers[model_type];
+  const SyncSessionSnapshot& snap = GetLastSessionSnapshot();
+  return snap.download_progress_markers()[model_type];
 }
 
 std::string ProfileSyncServiceHarness::GetClientInfoString(
@@ -985,38 +978,34 @@ std::string ProfileSyncServiceHarness::GetClientInfoString(
   std::stringstream os;
   os << profile_debug_name_ << ": " << message << ": ";
   if (service()) {
-    const SyncSessionSnapshot* snap = GetLastSessionSnapshot();
+    const SyncSessionSnapshot& snap = GetLastSessionSnapshot();
     const ProfileSyncService::Status& status = GetStatus();
-    if (snap) {
-      // Capture select info from the sync session snapshot and syncer status.
-      os << "has_more_to_sync: "
-         << snap->has_more_to_sync
-         << ", has_unsynced_items: "
-         << service()->HasUnsyncedItems()
-         << ", unsynced_count: "
-         << snap->unsynced_count
-         << ", encryption conflicts: "
-         << snap->num_encryption_conflicts
-         << ", hierarchy conflicts: "
-         << snap->num_hierarchy_conflicts
-         << ", simple conflicts: "
-         << snap->num_simple_conflicts
-         << ", server conflicts: "
-         << snap->num_server_conflicts
-         << ", num_updates_downloaded : "
-         << snap->syncer_status.num_updates_downloaded_total
-         << ", passphrase_required_reason: "
-         << sync_api::PassphraseRequiredReasonToString(
-             service()->passphrase_required_reason())
-         << ", notifications_enabled: "
-         << status.notifications_enabled
-         << ", service_is_pushing_changes: "
-         << ServiceIsPushingChanges()
-         << ", has_pending_backend_migration: "
-         << HasPendingBackendMigration();
-    } else {
-      os << "Sync session snapshot not available";
-    }
+    // Capture select info from the sync session snapshot and syncer status.
+    os << "has_more_to_sync: "
+       << snap.has_more_to_sync()
+       << ", has_unsynced_items: "
+       << service()->HasUnsyncedItems()
+       << ", unsynced_count: "
+       << snap.unsynced_count()
+       << ", encryption conflicts: "
+       << snap.num_encryption_conflicts()
+       << ", hierarchy conflicts: "
+       << snap.num_hierarchy_conflicts()
+       << ", simple conflicts: "
+       << snap.num_simple_conflicts()
+       << ", server conflicts: "
+       << snap.num_server_conflicts()
+       << ", num_updates_downloaded : "
+       << snap.syncer_status().num_updates_downloaded_total
+       << ", passphrase_required_reason: "
+       << sync_api::PassphraseRequiredReasonToString(
+           service()->passphrase_required_reason())
+       << ", notifications_enabled: "
+       << status.notifications_enabled
+       << ", service_is_pushing_changes: "
+       << ServiceIsPushingChanges()
+       << ", has_pending_backend_migration: "
+       << HasPendingBackendMigration();
   } else {
     os << "Sync service not available";
   }
@@ -1052,7 +1041,7 @@ bool ProfileSyncServiceHarness::WaitForTypeEncryption(
   // TODO(rlarocque): Figure out a less brittle way of detecting this.
   if (IsTypeEncrypted(type) &&
       IsFullySynced() &&
-      GetLastSessionSnapshot()->num_encryption_conflicts == 0) {
+      GetLastSessionSnapshot().num_encryption_conflicts() == 0) {
     // Encryption is already complete for |type|; do not wait.
     return true;
   }
@@ -1092,7 +1081,7 @@ bool ProfileSyncServiceHarness::IsTypePreferred(syncable::ModelType type) {
 }
 
 size_t ProfileSyncServiceHarness::GetNumEntries() const {
-  return GetLastSessionSnapshot()->num_entries;
+  return GetLastSessionSnapshot().num_entries();
 }
 
 size_t ProfileSyncServiceHarness::GetNumDatatypes() const {
diff --git a/chrome/browser/sync/profile_sync_service_harness.h b/chrome/browser/sync/profile_sync_service_harness.h
index 48de1d4..7ae069c 100644
--- a/chrome/browser/sync/profile_sync_service_harness.h
+++ b/chrome/browser/sync/profile_sync_service_harness.h
@@ -20,9 +20,9 @@
 class Profile;
 
 namespace browser_sync {
-  namespace sessions {
-    struct SyncSessionSnapshot;
-  }
+namespace sessions {
+class SyncSessionSnapshot;
+}
 }
 
 // An instance of this class is basically our notion of a "sync client" for
@@ -161,8 +161,7 @@ class ProfileSyncServiceHarness
   bool DisableSyncForAllDatatypes();
 
   // Returns a snapshot of the current sync session.
-  const browser_sync::sessions::SyncSessionSnapshot*
-      GetLastSessionSnapshot() const;
+  browser_sync::sessions::SyncSessionSnapshot GetLastSessionSnapshot() const;
 
   // Encrypt the datatype |type|. This method will block while the sync backend
   // host performs the encryption or a timeout is reached.
@@ -290,7 +289,8 @@ class ProfileSyncServiceHarness
                                     const std::string& reason);
 
   // A helper for implementing IsDataSynced() and IsFullySynced().
-  bool IsDataSyncedImpl(const browser_sync::sessions::SyncSessionSnapshot*);
+  bool IsDataSyncedImpl(
+      const browser_sync::sessions::SyncSessionSnapshot& snapshot);
 
   // Returns true if the sync client has no unsynced items.
   bool IsDataSynced();
diff --git a/chrome/browser/sync/profile_sync_service_mock.h b/chrome/browser/sync/profile_sync_service_mock.h
index bcad588..68e9700 100644
--- a/chrome/browser/sync/profile_sync_service_mock.h
+++ b/chrome/browser/sync/profile_sync_service_mock.h
@@ -74,7 +74,7 @@ class ProfileSyncServiceMock : public ProfileSyncService {
   MOCK_CONST_METHOD0(GetPreferredDataTypes, syncable::ModelTypeSet());
   MOCK_CONST_METHOD0(GetRegisteredDataTypes, syncable::ModelTypeSet());
   MOCK_CONST_METHOD0(GetLastSessionSnapshot,
-                     const browser_sync::sessions::SyncSessionSnapshot*());
+                     browser_sync::sessions::SyncSessionSnapshot());
 
   MOCK_METHOD0(QueryDetailedSyncStatus,
                browser_sync::SyncBackendHost::Status());
diff --git a/chrome/browser/sync/retry_verifier.cc b/chrome/browser/sync/retry_verifier.cc
index 0fa3843..b7f395b 100644
--- a/chrome/browser/sync/retry_verifier.cc
+++ b/chrome/browser/sync/retry_verifier.cc
@@ -81,7 +81,7 @@ RetryVerifier::~RetryVerifier() {
 void RetryVerifier::Initialize(
     const browser_sync::sessions::SyncSessionSnapshot& snap) {
   retry_count_ = 0;
-  last_sync_time_ = snap.sync_start_time;
+  last_sync_time_ = snap.sync_start_time();
   FillDelayTable(delay_table_, kMaxRetry);
   done_ = false;
   success_ = false;
@@ -91,9 +91,9 @@ void RetryVerifier::VerifyRetryInterval(
     const browser_sync::sessions::SyncSessionSnapshot& snap) {
   DCHECK(retry_count_ < kMaxRetry);
   if (retry_count_ == 0) {
-    if (snap.sync_start_time != last_sync_time_) {
+    if (snap.sync_start_time() != last_sync_time_) {
       retry_count_++;
-      last_sync_time_ = snap.sync_start_time;
+      last_sync_time_ = snap.sync_start_time();
     }
     success_ = true;
     return;
@@ -101,10 +101,10 @@ void RetryVerifier::VerifyRetryInterval(
 
   // Check if the sync start time has changed. If so indicates a new sync
   // has taken place.
-  if (snap.sync_start_time != last_sync_time_) {
-    base::TimeDelta delta = snap.sync_start_time - last_sync_time_;
+  if (snap.sync_start_time() != last_sync_time_) {
+    base::TimeDelta delta = snap.sync_start_time() - last_sync_time_;
     success_ = IsRetryOnTime(delay_table_,retry_count_ -1, delta);
-    last_sync_time_ = snap.sync_start_time;
+    last_sync_time_ = snap.sync_start_time();
     ++retry_count_;
     done_ = (retry_count_ >= kMaxRetry);
     return;
diff --git a/chrome/browser/sync/retry_verifier.h b/chrome/browser/sync/retry_verifier.h
index 755dab9..95023e2 100644
--- a/chrome/browser/sync/retry_verifier.h
+++ b/chrome/browser/sync/retry_verifier.h
@@ -9,12 +9,11 @@
 #include "base/time.h"
 
 namespace browser_sync {
+
 namespace sessions {
-struct SyncSessionSnapshot;
+class SyncSessionSnapshot;
 }  // namespace sessions
-}  // namespace browser_sync
 
-namespace browser_sync {
 // The minimum and maximum wait times for a retry. The actual retry would take
 // place somewhere in this range. The algorithm that calculates the retry wait
 // time uses rand functions.
@@ -47,5 +46,7 @@ class RetryVerifier {
   bool done_;
   DISALLOW_COPY_AND_ASSIGN(RetryVerifier);
 };
+
 }  // namespace browser_sync
+
 #endif  // CHROME_BROWSER_SYNC_RETRY_VERIFIER_H_
diff --git a/chrome/browser/sync/sync_ui_util.cc b/chrome/browser/sync/sync_ui_util.cc
index a4ba0ae..9a8307a 100644
--- a/chrome/browser/sync/sync_ui_util.cc
+++ b/chrome/browser/sync/sync_ui_util.cc
@@ -520,7 +520,7 @@ void ConstructAboutInformation(ProfileSyncService* service,
         service->QueryDetailedSyncStatus());
 
     // This is a cache of the last snapshot of type SYNC_CYCLE_ENDED where
-    // !snapshot->has_more_to_sync.  In other words, it's the last in this
+    // !snapshot.has_more_to_sync().  In other words, it's the last in this
     // series of sync cycles.  The series ends only when we've done all we can
     // to resolve conflicts and there is nothing left to commit, or an error
     // occurs.
@@ -530,9 +530,10 @@ void ConstructAboutInformation(ProfileSyncService* service,
     // the values from a single sync cycle.
     //
     // |snapshot| could be NULL if sync is not yet initialized.
-    const browser_sync::sessions::SyncSessionSnapshot* snapshot =
+    const browser_sync::sessions::SyncSessionSnapshot& snapshot =
         service->sync_initialized() ?
-        service->GetLastSessionSnapshot() : NULL;
+        service->GetLastSessionSnapshot() :
+        browser_sync::sessions::SyncSessionSnapshot();
 
     sync_ui_util::AddStringSyncDetails(sync_summary, "Summary",
                                        service->QuerySyncStatusSummary());
@@ -574,10 +575,8 @@ void ConstructAboutInformation(ProfileSyncService* service,
 
     // Network status indicators.
     ListValue* network = AddSyncDetailsSection(details, "Network");
-    if (snapshot) {
-      sync_ui_util::AddBoolSyncDetail(network, "Throttled",
-                                      snapshot->is_silenced);
-    }
+    sync_ui_util::AddBoolSyncDetail(network, "Throttled",
+                                    snapshot.is_silenced());
     sync_ui_util::AddBoolSyncDetail(network, "Notifications Enabled",
                                     full_status.notifications_enabled);
 
@@ -608,22 +607,20 @@ void ConstructAboutInformation(ProfileSyncService* service,
 
     ListValue* cycles = AddSyncDetailsSection(
         details, "Status from Last Completed Session");
-    if (snapshot) {
-      sync_ui_util::AddStringSyncDetails(
-          cycles, "Sync Source",
-          browser_sync::GetUpdatesSourceString(
-          snapshot->source.updates_source));
-      sync_ui_util::AddStringSyncDetails(
-          cycles, "Download Updates",
-          GetSyncerErrorString(snapshot->errors.last_download_updates_result));
-      sync_ui_util::AddStringSyncDetails(
-          cycles, "Post Commit",
-          GetSyncerErrorString(snapshot->errors.last_post_commit_result));
-      sync_ui_util::AddStringSyncDetails(
-          cycles, "Process Commit Response",
-          GetSyncerErrorString(
-              snapshot->errors.last_process_commit_response_result));
-    }
+    sync_ui_util::AddStringSyncDetails(
+        cycles, "Sync Source",
+        browser_sync::GetUpdatesSourceString(
+        snapshot.source().updates_source));
+    sync_ui_util::AddStringSyncDetails(
+        cycles, "Download Updates",
+        GetSyncerErrorString(snapshot.errors().last_download_updates_result));
+    sync_ui_util::AddStringSyncDetails(
+        cycles, "Post Commit",
+        GetSyncerErrorString(snapshot.errors().last_post_commit_result));
+    sync_ui_util::AddStringSyncDetails(
+        cycles, "Process Commit Response",
+        GetSyncerErrorString(
+            snapshot.errors().last_process_commit_response_result));
 
     // Strictly increasing counters.
     ListValue* counters = AddSyncDetailsSection(details, "Running Totals");
@@ -697,24 +694,20 @@ void ConstructAboutInformation(ProfileSyncService* service,
 
     ListValue* transient_session = AddSyncDetailsSection(
         details, "Transient Counters (last cycle of last completed session)");
-    if (snapshot) {
-      sync_ui_util::AddIntSyncDetail(
-          transient_session, "Updates Downloaded",
-          snapshot->syncer_status.num_updates_downloaded_total);
-      sync_ui_util::AddIntSyncDetail(
-          transient_session, "Committed Count",
-          snapshot->syncer_status.num_successful_commits);
-    }
-
-    if (snapshot) {
-      // This counter is stale.  The warnings related to the snapshot still
-      // apply, see the comments near call to GetLastSessionSnapshot() above.
-      // Also, because this is updated only following a complete sync cycle,
-      // local changes affecting this count will not be displayed until the
-      // syncer has attempted to commit those changes.
-      sync_ui_util::AddIntSyncDetail(transient_session, "Entries",
-                                     snapshot->num_entries);
-    }
+    sync_ui_util::AddIntSyncDetail(
+        transient_session, "Updates Downloaded",
+        snapshot.syncer_status().num_updates_downloaded_total);
+    sync_ui_util::AddIntSyncDetail(
+        transient_session, "Committed Count",
+        snapshot.syncer_status().num_successful_commits);
+
+    // This counter is stale.  The warnings related to the snapshot still
+    // apply, see the comments near call to GetLastSessionSnapshot() above.
+    // Also, because this is updated only following a complete sync cycle,
+    // local changes affecting this count will not be displayed until the
+    // syncer has attempted to commit those changes.
+    sync_ui_util::AddIntSyncDetail(transient_session, "Entries",
+                                   snapshot.num_entries());
 
     // Now set the actionable errors.
     if ((full_status.sync_protocol_error.error_type !=
diff --git a/chrome/browser/sync/test/integration/two_client_bookmarks_sync_test.cc b/chrome/browser/sync/test/integration/two_client_bookmarks_sync_test.cc
index f1ea473..ba4ead5 100644
--- a/chrome/browser/sync/test/integration/two_client_bookmarks_sync_test.cc
+++ b/chrome/browser/sync/test/integration/two_client_bookmarks_sync_test.cc
@@ -1815,8 +1815,8 @@ IN_PROC_BROWSER_TEST_F(TwoClientBookmarksSyncTest,
   ASSERT_TRUE(IsEncrypted(0, syncable::BOOKMARKS));
   ASSERT_TRUE(IsEncrypted(1, syncable::BOOKMARKS));
   ASSERT_TRUE(GetClient(1)->service()->IsPassphraseRequired());
-  ASSERT_GT(GetClient(1)->GetLastSessionSnapshot()->
-      num_encryption_conflicts, 3);  // The encrypted nodes.
+  ASSERT_GT(GetClient(1)->GetLastSessionSnapshot().num_encryption_conflicts(),
+            3);  // The encrypted nodes.
 
   // Client 1 adds bookmarks between the first two and between the second two.
   ASSERT_TRUE(AddURL(0, 1, IndexedURLTitle(3), GURL(IndexedURL(3))) != NULL);
@@ -1830,15 +1830,15 @@ IN_PROC_BROWSER_TEST_F(TwoClientBookmarksSyncTest,
   ASSERT_TRUE(GetClient(1)->AwaitPassphraseAccepted());
   ASSERT_TRUE(AwaitQuiescence());
   EXPECT_TRUE(AllModelsMatch());
-  ASSERT_EQ(0, GetClient(1)->GetLastSessionSnapshot()->
-      num_encryption_conflicts);
+  ASSERT_EQ(0,
+            GetClient(1)->GetLastSessionSnapshot().num_encryption_conflicts());
 
   // Ensure everything is syncing normally by appending a final bookmark.
   ASSERT_TRUE(AddURL(1, 5, IndexedURLTitle(5), GURL(IndexedURL(5))) != NULL);
   ASSERT_TRUE(GetClient(1)->AwaitMutualSyncCycleCompletion(GetClient(0)));
   EXPECT_TRUE(AllModelsMatch());
-  ASSERT_EQ(0, GetClient(1)->GetLastSessionSnapshot()->
-      num_encryption_conflicts);
+  ASSERT_EQ(0,
+            GetClient(1)->GetLastSessionSnapshot().num_encryption_conflicts());
 }
 
 // Deliberately racy rearranging of bookmarks to test that our conflict resolver
diff --git a/chrome/browser/sync/test_profile_sync_service.cc b/chrome/browser/sync/test_profile_sync_service.cc
index 83e04c5..500a838 100644
--- a/chrome/browser/sync/test_profile_sync_service.cc
+++ b/chrome/browser/sync/test_profile_sync_service.cc
@@ -49,8 +49,8 @@ void SyncBackendHostForProfileSyncTest::
   syncable::ModelTypeSet sync_ended;
   if (!fail_initial_download_)
     sync_ended = syncable::ModelTypeSet::All();
-  std::string download_progress_markers[syncable::MODEL_TYPE_COUNT];
-  HandleSyncCycleCompletedOnFrontendLoop(new SyncSessionSnapshot(
+  syncable::ModelTypePayloadMap download_progress_markers;
+  HandleSyncCycleCompletedOnFrontendLoop(SyncSessionSnapshot(
       SyncerStatus(), ErrorCounters(), 0, false,
       sync_ended, download_progress_markers, false, false, 0, 0, 0, 0, 0,
       false, SyncSourceInfo(), false, 0, base::Time::Now(), false));
@@ -92,8 +92,8 @@ void SyncBackendHostForProfileSyncTest::StartConfiguration(
 
     if (!fail_initial_download_)
       sync_ended.Put(syncable::NIGORI);
-    std::string download_progress_markers[syncable::MODEL_TYPE_COUNT];
-    HandleSyncCycleCompletedOnFrontendLoop(new SyncSessionSnapshot(
+    syncable::ModelTypePayloadMap download_progress_markers;
+    HandleSyncCycleCompletedOnFrontendLoop(SyncSessionSnapshot(
         SyncerStatus(), ErrorCounters(), 0, false,
         sync_ended, download_progress_markers, false, false, 0, 0, 0, 0, 0,
         false, SyncSourceInfo(), false, 0, base::Time::Now(), false));