[Sync] Refactoring polling to be reliable.

sync/engine/syncer.cc

Index: sync/engine/syncer.cc
diff --git a/sync/engine/syncer.cc b/sync/engine/syncer.cc
index ac4688117d4caecaee71a29437d7fe4c7c300df2..0b6bed27b0d5bbec52c5a27df28a68086276ce52 100644
--- a/sync/engine/syncer.cc
+++ b/sync/engine/syncer.cc
@@ -4,6 +4,7 @@
 
 #include "sync/engine/syncer.h"
 
+#include "base/auto_reset.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ -45,7 +46,8 @@ using sessions::SyncSession;
 using sessions::NudgeTracker;
 
 Syncer::Syncer(syncer::CancelationSignal* cancelation_signal)
-    : cancelation_signal_(cancelation_signal) {
+    : cancelation_signal_(cancelation_signal),
+      is_syncing_(false) {
 }
 
 Syncer::~Syncer() {}
@@ -54,9 +56,14 @@ bool Syncer::ExitRequested() {
   return cancelation_signal_->IsSignalled();
 }
 
+bool Syncer::IsSyncing() const {
+  return is_syncing_;
+}
+
 bool Syncer::NormalSyncShare(ModelTypeSet request_types,
                              NudgeTracker* nudge_tracker,
                              SyncSession* session) {
+  base::AutoReset<bool> is_syncing(&is_syncing_, true);
   HandleCycleBegin(session);
   if (nudge_tracker->IsGetUpdatesRequired() ||
       session->context()->ShouldFetchUpdatesBeforeCommit()) {
@@ -88,6 +95,7 @@ bool Syncer::ConfigureSyncShare(
     ModelTypeSet request_types,
     sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source,
     SyncSession* session) {
+  base::AutoReset<bool> is_syncing(&is_syncing_, true);
   VLOG(1) << "Configuring types " << ModelTypeSetToString(request_types);
   HandleCycleBegin(session);
   ConfigureGetUpdatesDelegate configure_delegate(source);
@@ -104,6 +112,7 @@ bool Syncer::ConfigureSyncShare(
 
 bool Syncer::PollSyncShare(ModelTypeSet request_types,
                            SyncSession* session) {
+  base::AutoReset<bool> is_syncing(&is_syncing_, true);
   VLOG(1) << "Polling types " << ModelTypeSetToString(request_types);
   HandleCycleBegin(session);
   PollGetUpdatesDelegate poll_delegate;
@@ -202,7 +211,12 @@ bool Syncer::HandleCycleEnd(
     sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source) {
   if (!ExitRequested()) {
     session->SendSyncCycleEndEventNotification(source);
-    return true;
+
+    bool success = !sessions::HasSyncerError(
+          session->status_controller().model_neutral_state());
+    if (success && source == sync_pb::GetUpdatesCallerInfo::PERIODIC)
+      session->mutable_status_controller()->UpdatePollTime();
+    return success;
   } else {
     return false;
   }