Use chrome/base synchronization primitives and threads instead of

pthreads in SyncerThread.  The old pthread impl can be used by
specifying --syncer-thread-pthreads for comparison until we
settle fully on the final impl (I have a MessageLoop-based impl
in progress).

The default SyncerThread is as close to the pthreads-impl semantics as
I could get, with one exception: it does not offer a time-out
when calling Stop(), because it greatly simplifies the implementation.
I first implemented it *with* the timeout, and for sake of
experimentation while this is in shuffle I am checking it in
as SyncerThreadTimedStop, available by using --syncer-thread-timed-stop. I'm not sure which we want ultimately, but it's useful to have around when building the MessageLoop based impl.

I had to refactor the interface slightly to allow multiple implementations,
I think it will be quite useful while working on the MessageLoop impl.

Added several tests to SyncerThreadUnittest, which all impls now pass (
just pass the command line flag to try each out).

TEST=SyncerThreadTest, SyncerThreadWithSyncerTest, integration tests

Review URL: http://codereview.chromium.org/214033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27117 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 1550 insertions, 248 deletions

diff --git a/chrome/browser/sync/engine/syncapi.cc b/chrome/browser/sync/engine/syncapi.cc
index f1ca43d..b9a8695 100644
--- a/chrome/browser/sync/engine/syncapi.cc
+++ b/chrome/browser/sync/engine/syncapi.cc
@@ -53,6 +53,7 @@ using browser_sync::Syncer;
 using browser_sync::SyncerEvent;
 using browser_sync::SyncerStatus;
 using browser_sync::SyncerThread;
+using browser_sync::SyncerThreadFactory;
 using browser_sync::UserSettings;
 using browser_sync::TalkMediator;
 using browser_sync::TalkMediatorImpl;
@@ -873,7 +874,7 @@ class SyncManager::SyncInternal {
   scoped_ptr<SyncAPIServerConnectionManager> connection_manager_;
 
   // The thread that runs the Syncer. Needs to be explicitly Start()ed.
-  scoped_ptr<SyncerThread> syncer_thread_;
+  scoped_refptr<SyncerThread> syncer_thread_;
 
   // Notification (xmpp) handler.
   scoped_ptr<TalkMediator> talk_mediator_;
@@ -1063,11 +1064,11 @@ bool SyncManager::SyncInternal::Init(
   // on the Syncer side, and |model_safe_worker| on the API client side.
   ModelSafeWorkerBridge* worker = new ModelSafeWorkerBridge(model_safe_worker);
 
-  syncer_thread_.reset(new SyncerThread(&command_channel_,
-                                        dir_manager(),
-                                        connection_manager(),
-                                        &allstatus_,
-                                        worker));
+  syncer_thread_ = SyncerThreadFactory::Create(&command_channel_,
+                                               dir_manager(),
+                                               connection_manager(),
+                                               &allstatus_,
+                                               worker);
   syncer_thread()->WatchTalkMediator(talk_mediator());
   allstatus()->WatchSyncerThread(syncer_thread());
 
diff --git a/chrome/browser/sync/engine/syncer_thread.cc b/chrome/browser/sync/engine/syncer_thread.cc
index a53ab93..0ef436b 100644
--- a/chrome/browser/sync/engine/syncer_thread.cc
+++ b/chrome/browser/sync/engine/syncer_thread.cc
@@ -1,7 +1,6 @@
 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
 #include "chrome/browser/sync/engine/syncer_thread.h"
 
 #include "build/build_config.h"
@@ -16,20 +15,23 @@
 #include <map>
 #include <queue>
 
+#include "base/command_line.h"
 #include "chrome/browser/sync/engine/auth_watcher.h"
 #include "chrome/browser/sync/engine/model_safe_worker.h"
 #include "chrome/browser/sync/engine/net/server_connection_manager.h"
 #include "chrome/browser/sync/engine/syncer.h"
+#include "chrome/browser/sync/engine/syncer_thread_pthreads.h"
+#include "chrome/browser/sync/engine/syncer_thread_timed_stop.h"
 #include "chrome/browser/sync/notifier/listener/talk_mediator.h"
 #include "chrome/browser/sync/notifier/listener/talk_mediator_impl.h"
 #include "chrome/browser/sync/syncable/directory_manager.h"
+#include "chrome/common/chrome_switches.h"
 
 using std::priority_queue;
 using std::min;
-
-static inline bool operator < (const timespec& a, const timespec& b) {
-  return a.tv_sec == b.tv_sec ? a.tv_nsec < b.tv_nsec : a.tv_sec < b.tv_sec;
-}
+using base::Time;
+using base::TimeDelta;
+using base::TimeTicks;
 
 namespace {
 
@@ -108,17 +110,56 @@ int UserIdleTime() {
 
 namespace browser_sync {
 
+SyncerThread* SyncerThreadFactory::Create(
+    ClientCommandChannel* command_channel,
+    syncable::DirectoryManager* mgr,
+    ServerConnectionManager* connection_manager, AllStatus* all_status,
+    ModelSafeWorker* model_safe_worker) {
+  const CommandLine* cmd = CommandLine::ForCurrentProcess();
+  if (cmd->HasSwitch(switches::kSyncerThreadTimedStop)) {
+    return new SyncerThreadTimedStop(command_channel, mgr, connection_manager,
+        all_status, model_safe_worker);
+  } else if (cmd->HasSwitch(switches::kSyncerThreadPthreads)) {
+    return new SyncerThreadPthreads(command_channel, mgr, connection_manager,
+        all_status, model_safe_worker);
+  } else {
+    // The default SyncerThread implementation, which does not time-out when
+    // Stop is called.
+    return new SyncerThread(command_channel, mgr, connection_manager,
+        all_status, model_safe_worker);
+  }
+}
+
 bool SyncerThread::NudgeSyncer(int milliseconds_from_now, NudgeSource source) {
-  MutexLock lock(&mutex_);
-  if (syncer_ == NULL) {
+  AutoLock lock(lock_);
+  if (vault_.syncer_ == NULL) {
     return false;
   }
   NudgeSyncImpl(milliseconds_from_now, source);
   return true;
 }
 
-void* RunSyncerThread(void* syncer_thread) {
-  return (reinterpret_cast<SyncerThread*>(syncer_thread))->ThreadMain();
+SyncerThread::SyncerThread()
+    : thread_main_started_(false, false),
+      thread_("SyncEngine_SyncerThread"),
+      vault_field_changed_(&lock_),
+      p2p_authenticated_(false),
+      p2p_subscribed_(false),
+      client_command_hookup_(NULL),
+      conn_mgr_hookup_(NULL),
+      allstatus_(NULL),
+      dirman_(NULL),
+      scm_(NULL),
+      syncer_short_poll_interval_seconds_(kDefaultShortPollIntervalSeconds),
+      syncer_long_poll_interval_seconds_(kDefaultLongPollIntervalSeconds),
+      syncer_polling_interval_(kDefaultShortPollIntervalSeconds),
+      syncer_max_interval_(kDefaultMaxPollIntervalMs),
+      talk_mediator_hookup_(NULL),
+      command_channel_(NULL),
+      directory_manager_hookup_(NULL),
+      syncer_events_(NULL),
+      model_safe_worker_(NULL),
+      disable_idle_detection_(false) {
 }
 
 SyncerThread::SyncerThread(
@@ -127,15 +168,14 @@ SyncerThread::SyncerThread(
     ServerConnectionManager* connection_manager,
     AllStatus* all_status,
     ModelSafeWorker* model_safe_worker)
-    : stop_syncer_thread_(false),
-      thread_running_(false),
-      connected_(false),
+    : thread_main_started_(false, false),
+      thread_("SyncEngine_SyncerThread"),
+      vault_field_changed_(&lock_),
       p2p_authenticated_(false),
       p2p_subscribed_(false),
       client_command_hookup_(NULL),
       conn_mgr_hookup_(NULL),
       allstatus_(all_status),
-      syncer_(NULL),
       dirman_(mgr),
       scm_(connection_manager),
       syncer_short_poll_interval_seconds_(kDefaultShortPollIntervalSeconds),
@@ -172,55 +212,76 @@ SyncerThread::~SyncerThread() {
   syncer_event_channel_.reset();
   directory_manager_hookup_.reset();
   syncer_events_.reset();
-  delete syncer_;
+  delete vault_.syncer_;
   talk_mediator_hookup_.reset();
-  CHECK(!thread_running_);
+  CHECK(!thread_.IsRunning());
 }
 
 // Creates and starts a syncer thread.
 // Returns true if it creates a thread or if there's currently a thread running
 // and false otherwise.
 bool SyncerThread::Start() {
-  MutexLock lock(&mutex_);
-  if (thread_running_) {
-    return true;
-  }
-  thread_running_ =
-    (0 == pthread_create(&thread_, NULL, RunSyncerThread, this));
-  if (thread_running_) {
-    pthread_detach(thread_);
+  {
+    AutoLock lock(lock_);
+    if (thread_.IsRunning()) {
+      return true;
+    }
+
+    if (!thread_.Start()) {
+      return false;
+    }
   }
-  return thread_running_;
+
+  thread_.message_loop()->PostTask(FROM_HERE, NewRunnableMethod(this,
+      &SyncerThread::ThreadMain));
+
+  // Wait for notification that our task makes it safely onto the message
+  // loop before returning, so the caller can't call Stop before we're
+  // actually up and running.  This is for consistency with the old pthread
+  // impl because pthread_create would do this in one step.
+  thread_main_started_.Wait();
+  LOG(INFO) << "SyncerThread started.";
+  return true;
 }
 
 // Stop processing. A max wait of at least 2*server RTT time is recommended.
 // Returns true if we stopped, false otherwise.
 bool SyncerThread::Stop(int max_wait) {
-  MutexLock lock(&mutex_);
-  if (!thread_running_)
-    return true;
-  stop_syncer_thread_ = true;
-  if (NULL != syncer_) {
-    // Try to early exit the syncer.
-    syncer_->RequestEarlyExit();
-  }
-  pthread_cond_broadcast(&changed_.condvar_);
-  timespec deadline = { time(NULL) + (max_wait / 1000), 0 };
-  do {
-    const int wait_result = max_wait < 0 ?
-      pthread_cond_wait(&changed_.condvar_, &mutex_.mutex_) :
-      pthread_cond_timedwait(&changed_.condvar_, &mutex_.mutex_,
-                             &deadline);
-    if (ETIMEDOUT == wait_result) {
-      LOG(ERROR) << "SyncerThread::Stop timed out. Problems likely.";
-      return false;
+  {
+    AutoLock lock(lock_);
+    // If the thread has been started, then we either already have or are about
+    // to enter ThreadMainLoop so we have to proceed with shutdown and wait for
+    // it to finish.  If the thread has not been started --and we now own the
+    // lock-- then we can early out because the caller has not called Start().
+    if (!thread_.IsRunning())
+      return true;
+
+    LOG(INFO) << "SyncerThread::Stop - setting ThreadMain exit condition to "
+              << "true (vault_.stop_syncer_thread_)";
+    // Exit the ThreadMainLoop once the syncer finishes (we tell it to exit
+    // below).
+    vault_.stop_syncer_thread_ = true;
+    if (NULL != vault_.syncer_) {
+      // Try to early exit the syncer itself, which could be looping inside
+      // SyncShare.
+      vault_.syncer_->RequestEarlyExit();
     }
-  } while (thread_running_);
+
+    // stop_syncer_thread_ is now true and the Syncer has been told to exit.
+    // We want to wake up all waiters so they can re-examine state. We signal,
+    // causing all waiters to try to re-acquire the lock, and then we release
+    // the lock, and join on our internal thread which should soon run off the
+    // end of ThreadMain.
+    vault_field_changed_.Broadcast();
+  }
+
+  // This will join, and finish when ThreadMain terminates.
+  thread_.Stop();
   return true;
 }
 
 void SyncerThread::WatchClientCommands(ClientCommandChannel* channel) {
-  PThreadScopedLock<PThreadMutex> lock(&mutex_);
+  AutoLock lock(lock_);
   client_command_hookup_.reset(NewEventListenerHookup(channel, this,
       &SyncerThread::HandleClientCommand));
 }
@@ -241,67 +302,89 @@ void SyncerThread::HandleClientCommand(ClientCommandChannel::EventType event) {
 }
 
 void SyncerThread::ThreadMainLoop() {
+  // This is called with lock_ acquired.
+  lock_.AssertAcquired();
+  LOG(INFO) << "In thread main loop.";
+
   // Use the short poll value by default.
-  int poll_seconds = syncer_short_poll_interval_seconds_;
+  TimeDelta poll_seconds =
+      TimeDelta::FromSeconds(syncer_short_poll_interval_seconds_);
   int user_idle_milliseconds = 0;
-  timespec last_sync_time = { 0 };
+  TimeTicks last_sync_time;
   bool initial_sync_for_thread = true;
   bool continue_sync_cycle = false;
 
-  while (!stop_syncer_thread_) {
-    if (!connected_) {
+  while (!vault_.stop_syncer_thread_) {
+    // The Wait()s in these conditionals using |vault_| are not TimedWait()s (as
+    // below) because we cannot poll until these conditions are met, so we wait
+    // indefinitely.
+    if (!vault_.connected_) {
       LOG(INFO) << "Syncer thread waiting for connection.";
-      while (!connected_ && !stop_syncer_thread_)
-        pthread_cond_wait(&changed_.condvar_, &mutex_.mutex_);
-      LOG_IF(INFO, connected_) << "Syncer thread found connection.";
+      while (!vault_.connected_ && !vault_.stop_syncer_thread_)
+        vault_field_changed_.Wait();
+      LOG_IF(INFO, vault_.connected_) << "Syncer thread found connection.";
       continue;
     }
 
-    if (syncer_ == NULL) {
+    if (vault_.syncer_ == NULL) {
       LOG(INFO) << "Syncer thread waiting for database initialization.";
-      while (syncer_ == NULL && !stop_syncer_thread_)
-        pthread_cond_wait(&changed_.condvar_, &mutex_.mutex_);
-      LOG_IF(INFO, !(syncer_ == NULL)) << "Syncer was found after DB started.";
+      while (vault_.syncer_ == NULL && !vault_.stop_syncer_thread_)
+        vault_field_changed_.Wait();
+      LOG_IF(INFO, !(vault_.syncer_ == NULL))
+          << "Syncer was found after DB started.";
       continue;
     }
 
-    timespec const next_poll = { last_sync_time.tv_sec + poll_seconds,
-                                 last_sync_time.tv_nsec };
-    const timespec wake_time =
-      !nudge_queue_.empty() && nudge_queue_.top().first < next_poll ?
-      nudge_queue_.top().first : next_poll;
-    LOG(INFO) << "wake time is " << wake_time.tv_sec;
-    LOG(INFO) << "next poll is " << next_poll.tv_sec;
-
-    const int error = pthread_cond_timedwait(&changed_.condvar_, &mutex_.mutex_,
-                                             &wake_time);
-    if (ETIMEDOUT != error) {
-      continue;  // Check all the conditions again.
+    const TimeTicks next_poll = last_sync_time + poll_seconds;
+    const TimeTicks end_wait =
+        !vault_.nudge_queue_.empty() &&
+        vault_.nudge_queue_.top().first < next_poll ?
+        vault_.nudge_queue_.top().first : next_poll;
+    LOG(INFO) << "end_wait is " << end_wait.ToInternalValue();
+    LOG(INFO) << "next_poll is " << next_poll.ToInternalValue();
+
+    // We block until the CV is signaled (e.g a control field changed, loss of
+    // network connection, nudge, spurious, etc), or the poll interval elapses.
+    TimeDelta sleep_time = end_wait - TimeTicks::Now();
+    if (sleep_time > TimeDelta::FromSeconds(0)) {
+      vault_field_changed_.TimedWait(sleep_time);
+
+      if (TimeTicks::Now() < end_wait) {
+        // Didn't timeout. Could be a spurious signal, or a signal corresponding
+        // to an actual change in one of our control fields.  By continuing here
+        // we perform the typical "always recheck conditions when signaled",
+        // (typically handled by a while(condition_not_met) cv.wait() construct)
+        // because we jump to the top of the loop.  The main difference is we
+        // recalculate the wait interval, but last_sync_time won't have changed.
+        // So if we were signaled by a nudge (for ex.) we'll grab the new nudge
+        // off the queue and wait for that delta.  If it was a spurious signal,
+        // we'll keep waiting for the same moment in time as we just were.
+        continue;
+       }
     }
 
-    const timespec now = GetPThreadAbsoluteTime(0);
-
     // Handle a nudge, caused by either a notification or a local bookmark
     // event.  This will also update the source of the following SyncMain call.
-    UpdateNudgeSource(now, &continue_sync_cycle, &initial_sync_for_thread);
+    UpdateNudgeSource(&continue_sync_cycle, &initial_sync_for_thread);
 
-    LOG(INFO) << "Calling Sync Main at time " << now.tv_sec;
-    SyncMain(syncer_);
-    last_sync_time = now;
+    LOG(INFO) << "Calling Sync Main at time " << Time::Now().ToInternalValue();
+    SyncMain(vault_.syncer_);
+    last_sync_time = TimeTicks::Now();
 
     LOG(INFO) << "Updating the next polling time after SyncMain";
-    poll_seconds = CalculatePollingWaitTime(allstatus_->status(),
-                                            poll_seconds,
-                                            &user_idle_milliseconds,
-                                            &continue_sync_cycle);
+    poll_seconds = TimeDelta::FromSeconds(CalculatePollingWaitTime(
+        allstatus_->status(), static_cast<int>(poll_seconds.InSeconds()),
+        &user_idle_milliseconds, &continue_sync_cycle));
   }
+
 }
 
 // We check how long the user's been idle and sync less often if the machine is
 // not in use. The aim is to reduce server load.
+// TODO(timsteele): Should use Time(Delta).
 int SyncerThread::CalculatePollingWaitTime(
     const AllStatus::Status& status,
-    int last_poll_wait,  // in s
+    int last_poll_wait,  // Time in seconds.
     int* user_idle_milliseconds,
     bool* continue_sync_cycle) {
   bool is_continuing_sync_cyle = *continue_sync_cycle;
@@ -352,30 +435,25 @@ int SyncerThread::CalculatePollingWaitTime(
   return actual_next_wait;
 }
 
-void* SyncerThread::ThreadMain() {
-  NameCurrentThreadForDebugging("SyncEngine_SyncerThread");
-  mutex_.Lock();
+void SyncerThread::ThreadMain() {
+  AutoLock lock(lock_);
+  // Signal Start() to let it know we've made it safely onto the message loop,
+  // and unblock it's caller.
+  thread_main_started_.Signal();
   ThreadMainLoop();
-  thread_running_ = false;
-  pthread_cond_broadcast(&changed_.condvar_);
-  mutex_.Unlock();
-  LOG(INFO) << "Syncer thread exiting.";
-  return 0;
+  LOG(INFO) << "Syncer thread ThreadMain is done.";
 }
 
 void SyncerThread::SyncMain(Syncer* syncer) {
   CHECK(syncer);
-  mutex_.Unlock();
+  AutoUnlock unlock(lock_);
   while (syncer->SyncShare()) {
     LOG(INFO) << "Looping in sync share";
   }
   LOG(INFO) << "Done looping in sync share";
-
-  mutex_.Lock();
 }
 
-void SyncerThread::UpdateNudgeSource(const timespec& now,
-                                     bool* continue_sync_cycle,
+void SyncerThread::UpdateNudgeSource(bool* continue_sync_cycle,
                                      bool* initial_sync) {
   bool nudged = false;
   NudgeSource nudge_source = kUnknown;
@@ -385,13 +463,14 @@ void SyncerThread::UpdateNudgeSource(const timespec& now,
   }
   // Update the nudge source if a new nudge has come through during the
   // previous sync cycle.
-  while (!nudge_queue_.empty() && !(now < nudge_queue_.top().first)) {
+  while (!vault_.nudge_queue_.empty() &&
+         TimeTicks::Now() >= vault_.nudge_queue_.top().first) {
     if (!nudged) {
-      nudge_source = nudge_queue_.top().second;
+      nudge_source = vault_.nudge_queue_.top().second;
       *continue_sync_cycle = false;  //  Reset the continuation token on nudge.
       nudged = true;
     }
-    nudge_queue_.pop();
+    vault_.nudge_queue_.pop();
   }
   SetUpdatesSource(nudged, nudge_source, initial_sync);
 }
@@ -422,11 +501,11 @@ void SyncerThread::SetUpdatesSource(bool nudged, NudgeSource nudge_source,
         break;
     }
   }
-  syncer_->set_updates_source(updates_source);
+  vault_.syncer_->set_updates_source(updates_source);
 }
 
 void SyncerThread::HandleSyncerEvent(const SyncerEvent& event) {
-  MutexLock lock(&mutex_);
+  AutoLock lock(lock_);
   channel()->NotifyListeners(event);
   if (SyncerEvent::REQUEST_SYNC_NUDGE != event.what_happened) {
     return;
@@ -438,33 +517,33 @@ void SyncerThread::HandleDirectoryManagerEvent(
     const syncable::DirectoryManagerEvent& event) {
   LOG(INFO) << "Handling a directory manager event";
   if (syncable::DirectoryManagerEvent::OPENED == event.what_happened) {
-    MutexLock lock(&mutex_);
+    AutoLock lock(lock_);
     LOG(INFO) << "Syncer starting up for: " << event.dirname;
     // The underlying database structure is ready, and we should create
     // the syncer.
-    CHECK(syncer_ == NULL);
-    syncer_ =
+    CHECK(vault_.syncer_ == NULL);
+    vault_.syncer_ =
         new Syncer(dirman_, event.dirname, scm_, model_safe_worker_.get());
 
-    syncer_->set_command_channel(command_channel_);
+    vault_.syncer_->set_command_channel(command_channel_);
     syncer_events_.reset(NewEventListenerHookup(
-        syncer_->channel(), this, &SyncerThread::HandleSyncerEvent));
-    pthread_cond_broadcast(&changed_.condvar_);
+        vault_.syncer_->channel(), this, &SyncerThread::HandleSyncerEvent));
+    vault_field_changed_.Broadcast();
   }
 }
 
 static inline void CheckConnected(bool* connected,
                                   HttpResponse::ServerConnectionCode code,
-                                  pthread_cond_t* condvar) {
+                                  ConditionVariable* condvar) {
   if (*connected) {
     if (HttpResponse::CONNECTION_UNAVAILABLE == code) {
       *connected = false;
-      pthread_cond_broadcast(condvar);
+      condvar->Broadcast();
     }
   } else {
     if (HttpResponse::SERVER_CONNECTION_OK == code) {
       *connected = true;
-      pthread_cond_broadcast(condvar);
+      condvar->Broadcast();
     }
   }
 }
@@ -472,16 +551,16 @@ static inline void CheckConnected(bool* connected,
 void SyncerThread::WatchConnectionManager(ServerConnectionManager* conn_mgr) {
   conn_mgr_hookup_.reset(NewEventListenerHookup(conn_mgr->channel(), this,
                          &SyncerThread::HandleServerConnectionEvent));
-  CheckConnected(&connected_, conn_mgr->server_status(),
-                 &changed_.condvar_);
+  CheckConnected(&vault_.connected_, conn_mgr->server_status(),
+                 &vault_field_changed_);
 }
 
 void SyncerThread::HandleServerConnectionEvent(
     const ServerConnectionEvent& event) {
   if (ServerConnectionEvent::STATUS_CHANGED == event.what_happened) {
-    MutexLock lock(&mutex_);
-    CheckConnected(&connected_, event.connection_code,
-                   &changed_.condvar_);
+    AutoLock lock(lock_);
+    CheckConnected(&vault_.connected_, event.connection_code,
+                   &vault_field_changed_);
   }
 }
 
@@ -513,10 +592,11 @@ int SyncerThread::CalculateSyncWaitTime(int last_interval, int user_idle_ms) {
 // Called with mutex_ already locked.
 void SyncerThread::NudgeSyncImpl(int milliseconds_from_now,
                                  NudgeSource source) {
-  const timespec nudge_time = GetPThreadAbsoluteTime(milliseconds_from_now);
+  const TimeTicks nudge_time = TimeTicks::Now() +
+      TimeDelta::FromMilliseconds(milliseconds_from_now);
   NudgeObject nudge_object(nudge_time, source);
-  nudge_queue_.push(nudge_object);
-  pthread_cond_broadcast(&changed_.condvar_);
+  vault_.nudge_queue_.push(nudge_object);
+  vault_field_changed_.Broadcast();
 }
 
 void SyncerThread::WatchTalkMediator(TalkMediator* mediator) {
@@ -528,7 +608,7 @@ void SyncerThread::WatchTalkMediator(TalkMediator* mediator) {
 }
 
 void SyncerThread::HandleTalkMediatorEvent(const TalkMediatorEvent& event) {
-  MutexLock lock(&mutex_);
+  AutoLock lock(lock_);
   switch (event.what_happened) {
     case TalkMediatorEvent::LOGIN_SUCCEEDED:
       LOG(INFO) << "P2P: Login succeeded.";
@@ -541,7 +621,7 @@ void SyncerThread::HandleTalkMediatorEvent(const TalkMediatorEvent& event) {
     case TalkMediatorEvent::SUBSCRIPTIONS_ON:
       LOG(INFO) << "P2P: Subscriptions successfully enabled.";
       p2p_subscribed_ = true;
-      if (NULL != syncer_) {
+      if (NULL != vault_.syncer_) {
         LOG(INFO) << "Subscriptions on.  Nudging syncer for initial push.";
         NudgeSyncImpl(0, kLocal);
       }
@@ -552,7 +632,7 @@ void SyncerThread::HandleTalkMediatorEvent(const TalkMediatorEvent& event) {
       break;
     case TalkMediatorEvent::NOTIFICATION_RECEIVED:
       LOG(INFO) << "P2P: Updates on server, pushing syncer";
-      if (NULL != syncer_) {
+      if (NULL != vault_.syncer_) {
         NudgeSyncImpl(0, kNotification);
       }
       break;
@@ -560,8 +640,9 @@ void SyncerThread::HandleTalkMediatorEvent(const TalkMediatorEvent& event) {
       break;
   }
 
-  if (NULL != syncer_) {
-    syncer_->set_notifications_enabled(p2p_authenticated_ && p2p_subscribed_);
+  if (NULL != vault_.syncer_) {
+    vault_.syncer_->set_notifications_enabled(
+        p2p_authenticated_ && p2p_subscribed_);
   }
 }
 
diff --git a/chrome/browser/sync/engine/syncer_thread.h b/chrome/browser/sync/engine/syncer_thread.h
index ca22969e..4d1ae95 100644
--- a/chrome/browser/sync/engine/syncer_thread.h
+++ b/chrome/browser/sync/engine/syncer_thread.h
@@ -3,7 +3,8 @@
 // found in the LICENSE file.
 //
 // A class to run the syncer on a thread.
-
+// This is the default implementation of SyncerThread whose Stop implementation
+// does not support a timeout, but is greatly simplified.
 #ifndef CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_H_
 #define CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_H_
 
@@ -13,11 +14,15 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/condition_variable.h"
+#include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
+#include "base/thread.h"
+#include "base/time.h"
+#include "base/waitable_event.h"
 #include "chrome/browser/sync/engine/all_status.h"
 #include "chrome/browser/sync/engine/client_command_channel.h"
 #include "chrome/browser/sync/util/event_sys-inl.h"
-#include "chrome/browser/sync/util/pthread_helpers.h"
 #include "testing/gtest/include/gtest/gtest_prod.h"  // For FRIEND_TEST
 
 class EventListenerHookup;
@@ -39,20 +44,42 @@ struct SyncerEvent;
 struct SyncerShutdownEvent;
 struct TalkMediatorEvent;
 
-class SyncerThread {
-  FRIEND_TEST(SyncerThreadTest, CalculateSyncWaitTime);
-  FRIEND_TEST(SyncerThreadTest, CalculatePollingWaitTime);
-
+class SyncerThreadFactory {
  public:
-  friend class SyncerThreadTest;
+  // Creates a SyncerThread based on the default (or user-overridden)
+  // implementation.  The thread does not start running until you call Start(),
+  // which will cause it to check-and-wait for certain conditions to be met
+  // (such as valid connection with Server established, syncable::Directory has
+  // been opened) before performing an intial sync with a server.  It uses
+  // |connection_manager| to detect valid connections, and |mgr| to detect the
+  // opening of a Directory, which will cause it to create a Syncer object for
+  // said Directory, and assign |model_safe_worker| to it.  |connection_manager|
+  // and |mgr| should outlive the SyncerThread.  You must stop the thread by
+  // calling Stop before destroying the object.  Stopping will first tear down
+  // the Syncer object, allowing it to finish work in progress, before joining
+  // the Stop-calling thread with the internal thread.
+  static SyncerThread* Create(ClientCommandChannel* command_channel,
+      syncable::DirectoryManager* mgr,
+      ServerConnectionManager* connection_manager, AllStatus* all_status,
+      ModelSafeWorker* model_safe_worker);
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(SyncerThreadFactory);
+};
 
+class SyncerThread : public base::RefCountedThreadSafe<SyncerThread> {
+  FRIEND_TEST(SyncerThreadTest, CalculateSyncWaitTime);
+  FRIEND_TEST(SyncerThreadTest, CalculatePollingWaitTime);
+  FRIEND_TEST(SyncerThreadWithSyncerTest, Polling);
+  FRIEND_TEST(SyncerThreadWithSyncerTest, Nudge);
+  friend class SyncerThreadWithSyncerTest;
+  friend class SyncerThreadFactory;
+public:
   enum NudgeSource {
     kUnknown = 0,
     kNotification,
     kLocal,
     kContinuation
   };
-
   // Server can overwrite these values via client commands.
   // Standard short poll. This is used when XMPP is off.
   static const int kDefaultShortPollIntervalSeconds = 60;
@@ -62,54 +89,106 @@ class SyncerThread {
   // longest possible poll interval.
   static const int kDefaultMaxPollIntervalMs = 30 * 60 * 1000;
 
-  SyncerThread(ClientCommandChannel* command_channel,
-      syncable::DirectoryManager* mgr,
-      ServerConnectionManager* connection_manager, AllStatus* all_status,
-      ModelSafeWorker* model_safe_worker);
-  ~SyncerThread();
+  virtual ~SyncerThread();
+
+  virtual void WatchConnectionManager(ServerConnectionManager* conn_mgr);
 
-  void WatchConnectionManager(ServerConnectionManager* conn_mgr);
-  // Creates and starts a syncer thread.
+  // Starts a syncer thread.
   // Returns true if it creates a thread or if there's currently a thread
   // running and false otherwise.
-  bool Start();
+  virtual bool Start();
 
-  // Stop processing. A max wait of at least 2*server RTT time is recommended.
-  // returns true if we stopped, false otherwise.
-  bool Stop(int max_wait);
+  // Stop processing. |max_wait| doesn't do anything in this version.
+  virtual bool Stop(int max_wait);
 
-  // Nudges the syncer to sync with a delay specified.  This API is for access
+  // Nudges the syncer to sync with a delay specified. This API is for access
   // from the SyncerThread's controller and will cause a mutex lock.
-  bool NudgeSyncer(int milliseconds_from_now, NudgeSource source);
+  virtual bool NudgeSyncer(int milliseconds_from_now, NudgeSource source);
 
   // Registers this thread to watch talk mediator events.
-  void WatchTalkMediator(TalkMediator* talk_mediator);
+  virtual void WatchTalkMediator(TalkMediator* talk_mediator);
 
-  void WatchClientCommands(ClientCommandChannel* channel);
+  virtual void WatchClientCommands(ClientCommandChannel* channel);
 
-  SyncerEventChannel* channel();
+  virtual SyncerEventChannel* channel();
 
- private:
-  // A few members to gate the rate at which we nudge the syncer.
-  enum {
-    kNudgeRateLimitCount = 6,
-    kNudgeRateLimitTime = 180,
-  };
+ protected:
+  SyncerThread();  // Necessary for temporary pthreads-based PIMPL impl.
+  SyncerThread(ClientCommandChannel* command_channel,
+      syncable::DirectoryManager* mgr,
+      ServerConnectionManager* connection_manager, AllStatus* all_status,
+      ModelSafeWorker* model_safe_worker);
+  virtual void ThreadMain();
+  void ThreadMainLoop();
 
-  // A queue of all scheduled nudges.  One insertion for every call to
-  // NudgeQueue().
-  typedef std::pair<timespec, NudgeSource> NudgeObject;
+  virtual void SetConnected(bool connected) {
+    DCHECK(!thread_.IsRunning());
+    vault_.connected_ = connected;
+  }
+
+  virtual void SetSyncerPollingInterval(base::TimeDelta interval) {
+    // TODO(timsteele): Use TimeDelta internally.
+    syncer_polling_interval_ = static_cast<int>(interval.InSeconds());
+  }
+  virtual void SetSyncerShortPollInterval(base::TimeDelta interval) {
+    // TODO(timsteele): Use TimeDelta internally.
+    syncer_short_poll_interval_seconds_ =
+        static_cast<int>(interval.InSeconds());
+  }
+
+  // Needed to emulate the behavior of pthread_create, which synchronously
+  // started the thread and set the value of thread_running_ to true.
+  // We can't quite match that because we asynchronously post the task,
+  // which opens a window for Stop to get called before the task actually
+  // makes it.  To prevent this, we block Start() until we're sure it's ok.
+  base::WaitableEvent thread_main_started_;
 
-  struct IsTimeSpecGreater {
+  // Handle of the running thread.
+  base::Thread thread_;
+
+  typedef std::pair<base::TimeTicks, NudgeSource> NudgeObject;
+
+  struct IsTimeTicksGreater {
     inline bool operator() (const NudgeObject& lhs, const NudgeObject& rhs) {
-      return lhs.first.tv_sec == rhs.first.tv_sec ?
-          lhs.first.tv_nsec > rhs.first.tv_nsec :
-          lhs.first.tv_sec > rhs.first.tv_sec;
+      return lhs.first > rhs.first;
     }
   };
 
   typedef std::priority_queue<NudgeObject, std::vector<NudgeObject>,
-                              IsTimeSpecGreater> NudgeQueue;
+                              IsTimeTicksGreater> NudgeQueue;
+
+  // Fields that are modified / accessed by multiple threads go in this struct
+  // for clarity and explicitness.
+  struct ProtectedFields {
+    // False when we want to stop the thread.
+    bool stop_syncer_thread_;
+
+    Syncer* syncer_;
+
+    // State of the server connection.
+    bool connected_;
+
+    // A queue of all scheduled nudges.  One insertion for every call to
+    // NudgeQueue().
+    NudgeQueue nudge_queue_;
+
+    ProtectedFields()
+        : stop_syncer_thread_(false), syncer_(NULL), connected_(false) {}
+  } vault_;
+
+  // Gets signaled whenever a thread outside of the syncer thread changes a
+  // protected field in the vault_.
+  ConditionVariable vault_field_changed_;
+
+  // Used to lock everything in |vault_|.
+  Lock lock_;
+
+ private:
+  // A few members to gate the rate at which we nudge the syncer.
+  enum {
+    kNudgeRateLimitCount = 6,
+    kNudgeRateLimitTime = 180,
+  };
 
   // Threshold multipler for how long before user should be considered idle.
   static const int kPollBackoffThresholdMultiplier = 10;
@@ -125,9 +204,6 @@ class SyncerThread {
 
   void HandleTalkMediatorEvent(const TalkMediatorEvent& event);
 
-  void* ThreadMain();
-  void ThreadMainLoop();
-
   void SyncMain(Syncer* syncer);
 
   // Calculates the next sync wait time in seconds.  last_poll_wait is the time
@@ -137,42 +213,24 @@ class SyncerThread {
   // continue_sync_cycle parameter is used to determine whether or not we are
   // calculating a polling wait time that is a continuation of an sync cycle
   // which terminated while the syncer still had work to do.
-  int CalculatePollingWaitTime(
+  virtual int CalculatePollingWaitTime(
       const AllStatus::Status& status,
       int last_poll_wait,  // in s
       int* user_idle_milliseconds,
       bool* continue_sync_cycle);
   // Helper to above function, considers effect of user idle time.
-  int CalculateSyncWaitTime(int last_wait, int user_idle_ms);
+  virtual int CalculateSyncWaitTime(int last_wait, int user_idle_ms);
 
   // Sets the source value of the controlled syncer's updates_source value.
   // The initial sync boolean is updated if read as a sentinel.  The following
   // two methods work in concert to achieve this goal.
-  void UpdateNudgeSource(const timespec& now, bool* continue_sync_cycle,
+  void UpdateNudgeSource(bool* continue_sync_cycle,
                          bool* initial_sync);
   void SetUpdatesSource(bool nudged, NudgeSource nudge_source,
                         bool* initial_sync);
 
   // For unit tests only.
-  void DisableIdleDetection() { disable_idle_detection_ = true; }
-
-  // False when we want to stop the thread.
-  bool stop_syncer_thread_;
-
-  // We use one mutex for all members except the channel.
-  PThreadMutex mutex_;
-  typedef PThreadScopedLock<PThreadMutex> MutexLock;
-
-  // Handle of the running thread.
-  pthread_t thread_;
-  bool thread_running_;
-
-  // Gets signaled whenever a thread outside of the syncer thread changes a
-  // member variable.
-  PThreadCondVar changed_;
-
-  // State of the server connection.
-  bool connected_;
+  virtual void DisableIdleDetection() { disable_idle_detection_ = true; }
 
   // State of the notification framework is tracked by these values.
   bool p2p_authenticated_;
@@ -182,8 +240,6 @@ class SyncerThread {
   scoped_ptr<EventListenerHookup> conn_mgr_hookup_;
   const AllStatus* allstatus_;
 
-  Syncer* syncer_;
-
   syncable::DirectoryManager* dirman_;
   ServerConnectionManager* scm_;
 
@@ -208,8 +264,6 @@ class SyncerThread {
   // this is called.
   void NudgeSyncImpl(int milliseconds_from_now, NudgeSource source);
 
-  NudgeQueue nudge_queue_;
-
   scoped_ptr<EventListenerHookup> talk_mediator_hookup_;
   ClientCommandChannel* const command_channel_;
   scoped_ptr<EventListenerHookup> directory_manager_hookup_;
@@ -228,4 +282,4 @@ class SyncerThread {
 
 }  // namespace browser_sync
 
-#endif  // CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_H_
+#endif  // CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_H_
\ No newline at end of file
diff --git a/chrome/browser/sync/engine/syncer_thread_pthreads.cc b/chrome/browser/sync/engine/syncer_thread_pthreads.cc
new file mode 100644
index 0000000..9fdfb21
--- /dev/null
+++ b/chrome/browser/sync/engine/syncer_thread_pthreads.cc
@@ -0,0 +1,578 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#include "chrome/browser/sync/engine/syncer_thread_pthreads.h"
+
+#include "build/build_config.h"
+
+#ifdef OS_MACOSX
+#include <CoreFoundation/CFNumber.h>
+#include <IOKit/IOTypes.h>
+#include <IOKit/IOKitLib.h>
+#endif
+
+#include <algorithm>
+#include <map>
+#include <queue>
+
+#include "chrome/browser/sync/engine/auth_watcher.h"
+#include "chrome/browser/sync/engine/model_safe_worker.h"
+#include "chrome/browser/sync/engine/net/server_connection_manager.h"
+#include "chrome/browser/sync/engine/syncer.h"
+#include "chrome/browser/sync/notifier/listener/talk_mediator.h"
+#include "chrome/browser/sync/notifier/listener/talk_mediator_impl.h"
+#include "chrome/browser/sync/syncable/directory_manager.h"
+
+using std::priority_queue;
+using std::min;
+
+static inline bool operator < (const timespec& a, const timespec& b) {
+  return a.tv_sec == b.tv_sec ? a.tv_nsec < b.tv_nsec : a.tv_sec < b.tv_sec;
+}
+
+namespace {
+
+// Returns the amount of time since the user last interacted with the computer,
+// in milliseconds
+int UserIdleTime() {
+#ifdef OS_WIN
+  LASTINPUTINFO last_input_info;
+  last_input_info.cbSize = sizeof(LASTINPUTINFO);
+
+  // Get time in windows ticks since system start of last activity.
+  BOOL b = ::GetLastInputInfo(&last_input_info);
+  if (b == TRUE)
+    return ::GetTickCount() - last_input_info.dwTime;
+#elif defined(OS_MACOSX)
+  // It would be great to do something like:
+  //
+  // return 1000 *
+  //     CGEventSourceSecondsSinceLastEventType(
+  //         kCGEventSourceStateCombinedSessionState,
+  //         kCGAnyInputEventType);
+  //
+  // Unfortunately, CGEvent* lives in ApplicationServices, and we're a daemon
+  // and can't link that high up the food chain. Thus this mucking in IOKit.
+
+  io_service_t hid_service =
+      IOServiceGetMatchingService(kIOMasterPortDefault,
+                                  IOServiceMatching("IOHIDSystem"));
+  if (!hid_service) {
+    LOG(WARNING) << "Could not obtain IOHIDSystem";
+    return 0;
+  }
+
+  CFTypeRef object = IORegistryEntryCreateCFProperty(hid_service,
+                                                     CFSTR("HIDIdleTime"),
+                                                     kCFAllocatorDefault,
+                                                     0);
+  if (!object) {
+    LOG(WARNING) << "Could not get IOHIDSystem's HIDIdleTime property";
+    IOObjectRelease(hid_service);
+    return 0;
+  }
+
+  int64 idle_time;  // in nanoseconds
+  Boolean success;
+  if (CFGetTypeID(object) == CFNumberGetTypeID()) {
+    success = CFNumberGetValue((CFNumberRef)object,
+                               kCFNumberSInt64Type,
+                               &idle_time);
+  } else {
+    LOG(WARNING) << "IOHIDSystem's HIDIdleTime property isn't a number!";
+  }
+
+  CFRelease(object);
+  IOObjectRelease(hid_service);
+
+  if (!success) {
+    LOG(WARNING) << "Could not get IOHIDSystem's HIDIdleTime property's value";
+    return 0;
+  } else {
+    return idle_time / 1000000;  // nano to milli
+  }
+#else
+  static bool was_logged = false;
+  if (!was_logged) {
+    was_logged = true;
+    LOG(INFO) << "UserIdleTime unimplemented on this platform, "
+        "synchronization will not throttle when user idle";
+  }
+#endif
+
+  return 0;
+}
+
+}  // namespace
+
+namespace browser_sync {
+
+SyncerThreadPthreads::SyncerThreadPthreads(
+    ClientCommandChannel* command_channel,
+    syncable::DirectoryManager* mgr,
+    ServerConnectionManager* connection_manager,
+    AllStatus* all_status, ModelSafeWorker* model_safe_worker)
+    : SyncerThread() {
+  impl_.reset(new SyncerThreadPthreadImpl(command_channel, mgr,
+      connection_manager, all_status, model_safe_worker));
+}
+
+bool SyncerThreadPthreadImpl::NudgeSyncer(int milliseconds_from_now,
+                                          SyncerThread::NudgeSource source) {
+  MutexLock lock(&mutex_);
+  if (syncer_ == NULL) {
+    return false;
+  }
+  NudgeSyncImpl(milliseconds_from_now, source);
+  return true;
+}
+
+void* RunSyncerThread(void* syncer_thread) {
+  return (reinterpret_cast<SyncerThreadPthreadImpl*>(
+      syncer_thread))->ThreadMain();
+}
+
+SyncerThreadPthreadImpl::SyncerThreadPthreadImpl(
+    ClientCommandChannel* command_channel,
+    syncable::DirectoryManager* mgr,
+    ServerConnectionManager* connection_manager,
+    AllStatus* all_status,
+    ModelSafeWorker* model_safe_worker)
+    : dirman_(mgr), scm_(connection_manager),
+      syncer_(NULL), syncer_events_(NULL), thread_running_(false),
+      syncer_short_poll_interval_seconds_(
+          SyncerThread::kDefaultShortPollIntervalSeconds),
+      syncer_long_poll_interval_seconds_(
+          SyncerThread::kDefaultLongPollIntervalSeconds),
+      syncer_polling_interval_(SyncerThread::kDefaultShortPollIntervalSeconds),
+      syncer_max_interval_(SyncerThread::kDefaultMaxPollIntervalMs),
+      stop_syncer_thread_(false), connected_(false), conn_mgr_hookup_(NULL),
+      p2p_authenticated_(false), p2p_subscribed_(false),
+      allstatus_(all_status), talk_mediator_hookup_(NULL),
+      command_channel_(command_channel), directory_manager_hookup_(NULL),
+      model_safe_worker_(model_safe_worker),
+      client_command_hookup_(NULL), disable_idle_detection_(false) {
+
+  SyncerEvent shutdown = { SyncerEvent::SHUTDOWN_USE_WITH_CARE };
+  syncer_event_channel_.reset(new SyncerEventChannel(shutdown));
+
+  if (dirman_) {
+    directory_manager_hookup_.reset(NewEventListenerHookup(
+        dirman_->channel(), this,
+        &SyncerThreadPthreadImpl::HandleDirectoryManagerEvent));
+  }
+
+  if (scm_) {
+    WatchConnectionManager(scm_);
+  }
+
+  if (command_channel_) {
+    WatchClientCommands(command_channel_);
+  }
+}
+
+SyncerThreadPthreadImpl::~SyncerThreadPthreadImpl() {
+  client_command_hookup_.reset();
+  conn_mgr_hookup_.reset();
+  syncer_event_channel_.reset();
+  directory_manager_hookup_.reset();
+  syncer_events_.reset();
+  delete syncer_;
+  talk_mediator_hookup_.reset();
+  CHECK(!thread_running_);
+}
+
+// Creates and starts a syncer thread.
+// Returns true if it creates a thread or if there's currently a thread running
+// and false otherwise.
+bool SyncerThreadPthreadImpl::Start() {
+  MutexLock lock(&mutex_);
+  if (thread_running_) {
+    return true;
+  }
+  thread_running_ =
+    (0 == pthread_create(&thread_, NULL, RunSyncerThread, this));
+  if (thread_running_) {
+    pthread_detach(thread_);
+  }
+  return thread_running_;
+}
+
+// Stop processing. A max wait of at least 2*server RTT time is recommended.
+// Returns true if we stopped, false otherwise.
+bool SyncerThreadPthreadImpl::Stop(int max_wait) {
+  MutexLock lock(&mutex_);
+  if (!thread_running_)
+    return true;
+  stop_syncer_thread_ = true;
+  if (NULL != syncer_) {
+    // Try to early exit the syncer.
+    syncer_->RequestEarlyExit();
+  }
+  pthread_cond_broadcast(&changed_.condvar_);
+  timespec deadline = { time(NULL) + (max_wait / 1000), 0 };
+  do {
+    const int wait_result = max_wait < 0 ?
+      pthread_cond_wait(&changed_.condvar_, &mutex_.mutex_) :
+      pthread_cond_timedwait(&changed_.condvar_, &mutex_.mutex_,
+                             &deadline);
+    if (ETIMEDOUT == wait_result) {
+      LOG(ERROR) << "SyncerThread::Stop timed out. Problems likely.";
+      return false;
+    }
+  } while (thread_running_);
+  return true;
+}
+
+void SyncerThreadPthreadImpl::WatchClientCommands(
+    ClientCommandChannel* channel) {
+  PThreadScopedLock<PThreadMutex> lock(&mutex_);
+  client_command_hookup_.reset(NewEventListenerHookup(channel, this,
+      &SyncerThreadPthreadImpl::HandleClientCommand));
+}
+
+void SyncerThreadPthreadImpl::HandleClientCommand(
+    ClientCommandChannel::EventType event) {
+  if (!event) {
+    return;
+  }
+
+  // Mutex not really necessary for these.
+  if (event->has_set_sync_poll_interval()) {
+    syncer_short_poll_interval_seconds_ = event->set_sync_poll_interval();
+  }
+
+  if (event->has_set_sync_long_poll_interval()) {
+    syncer_long_poll_interval_seconds_ = event->set_sync_long_poll_interval();
+  }
+}
+
+void SyncerThreadPthreadImpl::ThreadMainLoop() {
+  // Use the short poll value by default.
+  int poll_seconds = syncer_short_poll_interval_seconds_;
+  int user_idle_milliseconds = 0;
+  timespec last_sync_time = { 0 };
+  bool initial_sync_for_thread = true;
+  bool continue_sync_cycle = false;
+
+  while (!stop_syncer_thread_) {
+    if (!connected_) {
+      LOG(INFO) << "Syncer thread waiting for connection.";
+      while (!connected_ && !stop_syncer_thread_)
+        pthread_cond_wait(&changed_.condvar_, &mutex_.mutex_);
+      LOG_IF(INFO, connected_) << "Syncer thread found connection.";
+      continue;
+    }
+
+    if (syncer_ == NULL) {
+      LOG(INFO) << "Syncer thread waiting for database initialization.";
+      while (syncer_ == NULL && !stop_syncer_thread_)
+        pthread_cond_wait(&changed_.condvar_, &mutex_.mutex_);
+      LOG_IF(INFO, !(syncer_ == NULL)) << "Syncer was found after DB started.";
+      continue;
+    }
+
+    timespec const next_poll = { last_sync_time.tv_sec + poll_seconds,
+                                 last_sync_time.tv_nsec };
+    const timespec wake_time =
+      !nudge_queue_.empty() && nudge_queue_.top().first < next_poll ?
+      nudge_queue_.top().first : next_poll;
+    LOG(INFO) << "wake time is " << wake_time.tv_sec;
+    LOG(INFO) << "next poll is " << next_poll.tv_sec;
+
+    const int error = pthread_cond_timedwait(&changed_.condvar_, &mutex_.mutex_,
+                                             &wake_time);
+    if (ETIMEDOUT != error) {
+      continue;  // Check all the conditions again.
+    }
+
+    const timespec now = GetPThreadAbsoluteTime(0);
+
+    // Handle a nudge, caused by either a notification or a local bookmark
+    // event.  This will also update the source of the following SyncMain call.
+    UpdateNudgeSource(now, &continue_sync_cycle, &initial_sync_for_thread);
+
+    LOG(INFO) << "Calling Sync Main at time " << now.tv_sec;
+    SyncMain(syncer_);
+    last_sync_time = now;
+
+    LOG(INFO) << "Updating the next polling time after SyncMain";
+    poll_seconds = CalculatePollingWaitTime(allstatus_->status(),
+                                            poll_seconds,
+                                            &user_idle_milliseconds,
+                                            &continue_sync_cycle);
+  }
+}
+
+// We check how long the user's been idle and sync less often if the machine is
+// not in use. The aim is to reduce server load.
+int SyncerThreadPthreadImpl::CalculatePollingWaitTime(
+    const AllStatus::Status& status,
+    int last_poll_wait,  // in s
+    int* user_idle_milliseconds,
+    bool* continue_sync_cycle) {
+  bool is_continuing_sync_cyle = *continue_sync_cycle;
+  *continue_sync_cycle = false;
+
+  // Determine if the syncer has unfinished work to do from allstatus_.
+  const bool syncer_has_work_to_do =
+    status.updates_available > status.updates_received
+    || status.unsynced_count > 0;
+  LOG(INFO) << "syncer_has_work_to_do is " << syncer_has_work_to_do;
+
+  // First calculate the expected wait time, figuring in any backoff because of
+  // user idle time.  next_wait is in seconds
+  syncer_polling_interval_ = (!status.notifications_enabled) ?
+      syncer_short_poll_interval_seconds_ :
+      syncer_long_poll_interval_seconds_;
+  int default_next_wait = syncer_polling_interval_;
+  int actual_next_wait = default_next_wait;
+
+  if (syncer_has_work_to_do) {
+    // Provide exponential backoff due to consecutive errors, else attempt to
+    // complete the work as soon as possible.
+    if (!is_continuing_sync_cyle) {
+      actual_next_wait = AllStatus::GetRecommendedDelaySeconds(0);
+    } else {
+      actual_next_wait = AllStatus::GetRecommendedDelaySeconds(last_poll_wait);
+    }
+    *continue_sync_cycle = true;
+  } else if (!status.notifications_enabled) {
+    // Ensure that we start exponential backoff from our base polling
+    // interval when we are not continuing a sync cycle.
+    last_poll_wait = std::max(last_poll_wait, syncer_polling_interval_);
+
+    // Did the user start interacting with the computer again?
+    // If so, revise our idle time (and probably next_sync_time) downwards
+    int new_idle_time = disable_idle_detection_ ? 0 : UserIdleTime();
+    if (new_idle_time < *user_idle_milliseconds) {
+      *user_idle_milliseconds = new_idle_time;
+    }
+    actual_next_wait = CalculateSyncWaitTime(last_poll_wait * 1000,
+                                              *user_idle_milliseconds) / 1000;
+    DCHECK_GE(actual_next_wait, default_next_wait);
+  }
+
+  LOG(INFO) << "Sync wait: idle " << default_next_wait
+            << " non-idle or backoff " << actual_next_wait << ".";
+
+  return actual_next_wait;
+}
+
+void* SyncerThreadPthreadImpl::ThreadMain() {
+  NameCurrentThreadForDebugging("SyncEngine_SyncerThread");
+  mutex_.Lock();
+  ThreadMainLoop();
+  thread_running_ = false;
+  pthread_cond_broadcast(&changed_.condvar_);
+  mutex_.Unlock();
+  LOG(INFO) << "Syncer thread exiting.";
+  return 0;
+}
+
+void SyncerThreadPthreadImpl::SyncMain(Syncer* syncer) {
+  CHECK(syncer);
+  mutex_.Unlock();
+  while (syncer->SyncShare()) {
+    LOG(INFO) << "Looping in sync share";
+  }
+  LOG(INFO) << "Done looping in sync share";
+
+  mutex_.Lock();
+}
+
+void SyncerThreadPthreadImpl::UpdateNudgeSource(const timespec& now,
+                                     bool* continue_sync_cycle,
+                                     bool* initial_sync) {
+  bool nudged = false;
+  SyncerThread::NudgeSource nudge_source = SyncerThread::kUnknown;
+  // Has the previous sync cycle completed?
+  if (continue_sync_cycle) {
+    nudge_source = SyncerThread::kContinuation;
+  }
+  // Update the nudge source if a new nudge has come through during the
+  // previous sync cycle.
+  while (!nudge_queue_.empty() && !(now < nudge_queue_.top().first)) {
+    if (!nudged) {
+      nudge_source = nudge_queue_.top().second;
+      *continue_sync_cycle = false;  //  Reset the continuation token on nudge.
+      nudged = true;
+    }
+    nudge_queue_.pop();
+  }
+  SetUpdatesSource(nudged, nudge_source, initial_sync);
+}
+
+void SyncerThreadPthreadImpl::SetUpdatesSource(bool nudged,
+    SyncerThread::NudgeSource nudge_source, bool* initial_sync) {
+  sync_pb::GetUpdatesCallerInfo::GET_UPDATES_SOURCE updates_source =
+      sync_pb::GetUpdatesCallerInfo::UNKNOWN;
+  if (*initial_sync) {
+    updates_source = sync_pb::GetUpdatesCallerInfo::FIRST_UPDATE;
+    *initial_sync = false;
+  } else if (!nudged) {
+    updates_source = sync_pb::GetUpdatesCallerInfo::PERIODIC;
+  } else {
+    switch (nudge_source) {
+      case SyncerThread::kNotification:
+        updates_source = sync_pb::GetUpdatesCallerInfo::NOTIFICATION;
+        break;
+      case SyncerThread::kLocal:
+        updates_source = sync_pb::GetUpdatesCallerInfo::LOCAL;
+        break;
+      case SyncerThread::kContinuation:
+        updates_source = sync_pb::GetUpdatesCallerInfo::SYNC_CYCLE_CONTINUATION;
+        break;
+      case SyncerThread::kUnknown:
+      default:
+        updates_source = sync_pb::GetUpdatesCallerInfo::UNKNOWN;
+        break;
+    }
+  }
+  syncer_->set_updates_source(updates_source);
+}
+
+void SyncerThreadPthreadImpl::HandleSyncerEvent(const SyncerEvent& event) {
+  MutexLock lock(&mutex_);
+  channel()->NotifyListeners(event);
+  if (SyncerEvent::REQUEST_SYNC_NUDGE != event.what_happened) {
+    return;
+  }
+  NudgeSyncImpl(event.nudge_delay_milliseconds, SyncerThread::kUnknown);
+}
+
+void SyncerThreadPthreadImpl::HandleDirectoryManagerEvent(
+    const syncable::DirectoryManagerEvent& event) {
+  LOG(INFO) << "Handling a directory manager event";
+  if (syncable::DirectoryManagerEvent::OPENED == event.what_happened) {
+    MutexLock lock(&mutex_);
+    LOG(INFO) << "Syncer starting up for: " << event.dirname;
+    // The underlying database structure is ready, and we should create
+    // the syncer.
+    CHECK(syncer_ == NULL);
+    syncer_ =
+        new Syncer(dirman_, event.dirname, scm_, model_safe_worker_.get());
+
+    syncer_->set_command_channel(command_channel_);
+    syncer_events_.reset(NewEventListenerHookup(
+        syncer_->channel(), this, &SyncerThreadPthreadImpl::HandleSyncerEvent));
+    pthread_cond_broadcast(&changed_.condvar_);
+  }
+}
+
+static inline void CheckConnected(bool* connected,
+                                  HttpResponse::ServerConnectionCode code,
+                                  pthread_cond_t* condvar) {
+  if (*connected) {
+    if (HttpResponse::CONNECTION_UNAVAILABLE == code) {
+      *connected = false;
+      pthread_cond_broadcast(condvar);
+    }
+  } else {
+    if (HttpResponse::SERVER_CONNECTION_OK == code) {
+      *connected = true;
+      pthread_cond_broadcast(condvar);
+    }
+  }
+}
+
+void SyncerThreadPthreadImpl::WatchConnectionManager(
+    ServerConnectionManager* conn_mgr) {
+  conn_mgr_hookup_.reset(NewEventListenerHookup(conn_mgr->channel(), this,
+      &SyncerThreadPthreadImpl::HandleServerConnectionEvent));
+  CheckConnected(&connected_, conn_mgr->server_status(),
+                 &changed_.condvar_);
+}
+
+void SyncerThreadPthreadImpl::HandleServerConnectionEvent(
+    const ServerConnectionEvent& event) {
+  if (ServerConnectionEvent::STATUS_CHANGED == event.what_happened) {
+    MutexLock lock(&mutex_);
+    CheckConnected(&connected_, event.connection_code,
+                   &changed_.condvar_);
+  }
+}
+
+SyncerEventChannel* SyncerThreadPthreadImpl::channel() {
+  return syncer_event_channel_.get();
+}
+
+// Inputs and return value in milliseconds.
+int SyncerThreadPthreadImpl::CalculateSyncWaitTime(int last_interval,
+    int user_idle_ms) {
+  // syncer_polling_interval_ is in seconds
+  int syncer_polling_interval_ms = syncer_polling_interval_ * 1000;
+
+  // This is our default and lower bound.
+  int next_wait = syncer_polling_interval_ms;
+
+  // Get idle time, bounded by max wait.
+  int idle = min(user_idle_ms, syncer_max_interval_);
+
+  // If the user has been idle for a while, we'll start decreasing the poll
+  // rate.
+  if (idle >= kPollBackoffThresholdMultiplier * syncer_polling_interval_ms) {
+    next_wait = std::min(AllStatus::GetRecommendedDelaySeconds(
+        last_interval / 1000), syncer_max_interval_ / 1000) * 1000;
+  }
+
+  return next_wait;
+}
+
+// Called with mutex_ already locked.
+void SyncerThreadPthreadImpl::NudgeSyncImpl(int milliseconds_from_now,
+                                 SyncerThread::NudgeSource source) {
+  const timespec nudge_time = GetPThreadAbsoluteTime(milliseconds_from_now);
+  NudgeObject nudge_object(nudge_time, source);
+  nudge_queue_.push(nudge_object);
+  pthread_cond_broadcast(&changed_.condvar_);
+}
+
+void SyncerThreadPthreadImpl::WatchTalkMediator(TalkMediator* mediator) {
+  talk_mediator_hookup_.reset(
+      NewEventListenerHookup(
+          mediator->channel(),
+          this,
+          &SyncerThreadPthreadImpl::HandleTalkMediatorEvent));
+}
+
+void SyncerThreadPthreadImpl::HandleTalkMediatorEvent(
+    const TalkMediatorEvent& event) {
+  MutexLock lock(&mutex_);
+  switch (event.what_happened) {
+    case TalkMediatorEvent::LOGIN_SUCCEEDED:
+      LOG(INFO) << "P2P: Login succeeded.";
+      p2p_authenticated_ = true;
+      break;
+    case TalkMediatorEvent::LOGOUT_SUCCEEDED:
+      LOG(INFO) << "P2P: Login succeeded.";
+      p2p_authenticated_ = false;
+      break;
+    case TalkMediatorEvent::SUBSCRIPTIONS_ON:
+      LOG(INFO) << "P2P: Subscriptions successfully enabled.";
+      p2p_subscribed_ = true;
+      if (NULL != syncer_) {
+        LOG(INFO) << "Subscriptions on.  Nudging syncer for initial push.";
+        NudgeSyncImpl(0, SyncerThread::kLocal);
+      }
+      break;
+    case TalkMediatorEvent::SUBSCRIPTIONS_OFF:
+      LOG(INFO) << "P2P: Subscriptions are not enabled.";
+      p2p_subscribed_ = false;
+      break;
+    case TalkMediatorEvent::NOTIFICATION_RECEIVED:
+      LOG(INFO) << "P2P: Updates on server, pushing syncer";
+      if (NULL != syncer_) {
+        NudgeSyncImpl(0, SyncerThread::kNotification);
+      }
+      break;
+    default:
+      break;
+  }
+
+  if (NULL != syncer_) {
+    syncer_->set_notifications_enabled(p2p_authenticated_ && p2p_subscribed_);
+  }
+}
+
+}  // namespace browser_sync
\ No newline at end of file
diff --git a/chrome/browser/sync/engine/syncer_thread_pthreads.h b/chrome/browser/sync/engine/syncer_thread_pthreads.h
new file mode 100644
index 0000000..bebd8ed
--- /dev/null
+++ b/chrome/browser/sync/engine/syncer_thread_pthreads.h
@@ -0,0 +1,284 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// *THIS EXISTS FOR EXPERIMENTATION AND TESTING WHILE WE REPLACE PTHREADS
+//  WITH CHROME THREADS IN SYNC CODE*
+
+// A class to run the syncer on a thread.  Uses PIMPL to wrap the old, original
+// pthreads implementation of SyncerThread.
+#ifndef CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_PTHREADS_H_
+#define CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_PTHREADS_H_
+
+#include <list>
+#include <map>
+#include <queue>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "chrome/browser/sync/engine/all_status.h"
+#include "chrome/browser/sync/engine/client_command_channel.h"
+#include "chrome/browser/sync/util/event_sys-inl.h"
+#include "chrome/browser/sync/util/pthread_helpers.h"
+#include "chrome/browser/sync/engine/syncer_thread.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"  // For FRIEND_TEST
+
+class EventListenerHookup;
+
+namespace syncable {
+class DirectoryManager;
+struct DirectoryManagerEvent;
+}
+
+namespace browser_sync {
+
+class ModelSafeWorker;
+class ServerConnectionManager;
+class Syncer;
+class TalkMediator;
+class URLFactory;
+struct ServerConnectionEvent;
+struct SyncerEvent;
+struct SyncerShutdownEvent;
+struct TalkMediatorEvent;
+
+// The legacy implementation of SyncerThread using pthreads, kept around for
+// historical experimentation until a new version is finalized.
+class SyncerThreadPthreadImpl {
+ public:
+  virtual ~SyncerThreadPthreadImpl();
+
+  virtual void WatchConnectionManager(ServerConnectionManager* conn_mgr);
+  // Creates and starts a syncer thread.
+  // Returns true if it creates a thread or if there's currently a thread
+  // running and false otherwise.
+  virtual bool Start();
+
+  // Stop processing. A max wait of at least 2*server RTT time is recommended.
+  // returns true if we stopped, false otherwise.
+  virtual bool Stop(int max_wait);
+
+  // Nudges the syncer to sync with a delay specified.  This API is for access
+  // from the SyncerThread's controller and will cause a mutex lock.
+  virtual bool NudgeSyncer(int milliseconds_from_now,
+                           SyncerThread::NudgeSource source);
+
+  // Registers this thread to watch talk mediator events.
+  virtual void WatchTalkMediator(TalkMediator* talk_mediator);
+
+  virtual void WatchClientCommands(ClientCommandChannel* channel);
+
+  virtual SyncerEventChannel* channel();
+
+ private:
+  friend class SyncerThreadPthreads;
+  SyncerThreadPthreadImpl(ClientCommandChannel* command_channel,
+      syncable::DirectoryManager* mgr,
+      ServerConnectionManager* connection_manager, AllStatus* all_status,
+      ModelSafeWorker* model_safe_worker);
+
+  // A few members to gate the rate at which we nudge the syncer.
+  enum {
+    kNudgeRateLimitCount = 6,
+    kNudgeRateLimitTime = 180,
+  };
+
+  // A queue of all scheduled nudges.  One insertion for every call to
+  // NudgeQueue().
+  typedef std::pair<timespec, SyncerThread::NudgeSource> NudgeObject;
+
+  struct IsTimeSpecGreater {
+    inline bool operator() (const NudgeObject& lhs, const NudgeObject& rhs) {
+      return lhs.first.tv_sec == rhs.first.tv_sec ?
+          lhs.first.tv_nsec > rhs.first.tv_nsec :
+          lhs.first.tv_sec > rhs.first.tv_sec;
+    }
+  };
+
+  typedef std::priority_queue<NudgeObject, std::vector<NudgeObject>,
+                              IsTimeSpecGreater> NudgeQueue;
+
+  // Threshold multipler for how long before user should be considered idle.
+  static const int kPollBackoffThresholdMultiplier = 10;
+
+  friend void* RunSyncerThread(void* syncer_thread);
+  void* Run();
+  void HandleDirectoryManagerEvent(
+      const syncable::DirectoryManagerEvent& event);
+  void HandleSyncerEvent(const SyncerEvent& event);
+  void HandleClientCommand(ClientCommandChannel::EventType event);
+
+  void HandleServerConnectionEvent(const ServerConnectionEvent& event);
+
+  void HandleTalkMediatorEvent(const TalkMediatorEvent& event);
+
+  void* ThreadMain();
+  void ThreadMainLoop();
+
+  void SyncMain(Syncer* syncer);
+
+  // Calculates the next sync wait time in seconds.  last_poll_wait is the time
+  // duration of the previous polling timeout which was used.
+  // user_idle_milliseconds is updated by this method, and is a report of the
+  // full amount of time since the last period of activity for the user.  The
+  // continue_sync_cycle parameter is used to determine whether or not we are
+  // calculating a polling wait time that is a continuation of an sync cycle
+  // which terminated while the syncer still had work to do.
+  int CalculatePollingWaitTime(
+      const AllStatus::Status& status,
+      int last_poll_wait,  // in s
+      int* user_idle_milliseconds,
+      bool* continue_sync_cycle);
+  // Helper to above function, considers effect of user idle time.
+  int CalculateSyncWaitTime(int last_wait, int user_idle_ms);
+
+  // Sets the source value of the controlled syncer's updates_source value.
+  // The initial sync boolean is updated if read as a sentinel.  The following
+  // two methods work in concert to achieve this goal.
+  void UpdateNudgeSource(const timespec& now, bool* continue_sync_cycle,
+                         bool* initial_sync);
+  void SetUpdatesSource(bool nudged, SyncerThread::NudgeSource nudge_source,
+                        bool* initial_sync);
+
+  // For unit tests only.
+  void DisableIdleDetection() { disable_idle_detection_ = true; }
+
+  // False when we want to stop the thread.
+  bool stop_syncer_thread_;
+
+  // We use one mutex for all members except the channel.
+  PThreadMutex mutex_;
+  typedef PThreadScopedLock<PThreadMutex> MutexLock;
+
+  // Handle of the running thread.
+  pthread_t thread_;
+  bool thread_running_;
+
+  // Gets signaled whenever a thread outside of the syncer thread changes a
+  // member variable.
+  PThreadCondVar changed_;
+
+  // State of the server connection.
+  bool connected_;
+
+  // State of the notification framework is tracked by these values.
+  bool p2p_authenticated_;
+  bool p2p_subscribed_;
+
+  scoped_ptr<EventListenerHookup> client_command_hookup_;
+  scoped_ptr<EventListenerHookup> conn_mgr_hookup_;
+  const AllStatus* allstatus_;
+
+  Syncer* syncer_;
+
+  syncable::DirectoryManager* dirman_;
+  ServerConnectionManager* scm_;
+
+  // Modifiable versions of kDefaultLongPollIntervalSeconds which can be
+  // updated by the server.
+  int syncer_short_poll_interval_seconds_;
+  int syncer_long_poll_interval_seconds_;
+
+  // The time we wait between polls in seconds. This is used as lower bound on
+  // our wait time. Updated once per loop from the command line flag.
+  int syncer_polling_interval_;
+
+  // The upper bound on the nominal wait between polls in seconds. Note that
+  // this bounds the "nominal" poll interval, while the the actual interval
+  // also takes previous failures into account.
+  int syncer_max_interval_;
+
+  scoped_ptr<SyncerEventChannel> syncer_event_channel_;
+
+  // This causes syncer to start syncing ASAP. If the rate of requests is too
+  // high the request will be silently dropped.  mutex_ should be held when
+  // this is called.
+  void NudgeSyncImpl(int milliseconds_from_now,
+                     SyncerThread::NudgeSource source);
+
+  NudgeQueue nudge_queue_;
+
+  scoped_ptr<EventListenerHookup> talk_mediator_hookup_;
+  ClientCommandChannel* const command_channel_;
+  scoped_ptr<EventListenerHookup> directory_manager_hookup_;
+  scoped_ptr<EventListenerHookup> syncer_events_;
+
+  // Handles any tasks that will result in model changes (modifications of
+  // syncable::Entries). Pass this to the syncer created and managed by |this|.
+  // Only non-null in syncapi case.
+  scoped_ptr<ModelSafeWorker> model_safe_worker_;
+
+  // Useful for unit tests
+  bool disable_idle_detection_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncerThreadPthreadImpl);
+};
+
+// A new-version SyncerThread pimpl wrapper for the old legacy implementation.
+class SyncerThreadPthreads : public SyncerThread {
+  FRIEND_TEST(SyncerThreadTest, CalculateSyncWaitTime);
+  FRIEND_TEST(SyncerThreadTest, CalculatePollingWaitTime);
+  FRIEND_TEST(SyncerThreadWithSyncerTest, Polling);
+  FRIEND_TEST(SyncerThreadWithSyncerTest, Nudge);
+  friend class SyncerThreadWithSyncerTest;
+  friend class SyncerThreadFactory;
+ public:
+  virtual ~SyncerThreadPthreads() {}
+
+  virtual void WatchConnectionManager(ServerConnectionManager* conn_mgr) {
+    impl_->WatchConnectionManager(conn_mgr);
+  }
+  virtual bool Start() {
+    return impl_->Start();
+  }
+  virtual bool Stop(int max_wait) {
+    return impl_->Stop(max_wait);
+  }
+  virtual bool NudgeSyncer(int milliseconds_from_now, NudgeSource source) {
+    return impl_->NudgeSyncer(milliseconds_from_now, source);
+  }
+  virtual void WatchTalkMediator(TalkMediator* talk_mediator) {
+    impl_->WatchTalkMediator(talk_mediator);
+  }
+  virtual void WatchClientCommands(ClientCommandChannel* channel) {
+    impl_->WatchClientCommands(channel);
+  }
+  virtual SyncerEventChannel* channel() {
+    return impl_->channel();
+  }
+ protected:
+  SyncerThreadPthreads(ClientCommandChannel* command_channel,
+      syncable::DirectoryManager* mgr,
+      ServerConnectionManager* connection_manager, AllStatus* all_status,
+      ModelSafeWorker* model_safe_worker);
+  virtual void SetConnected(bool connected) {
+    impl_->connected_ = connected;
+  }
+  virtual void SetSyncerPollingInterval(int interval) {
+    impl_->syncer_polling_interval_ = interval;
+  }
+  virtual void SetSyncerShortPollInterval(base::TimeDelta interval) {
+    impl_->syncer_short_poll_interval_seconds_ = static_cast<int>(
+        interval.InSeconds());
+  }
+  virtual void DisableIdleDetection() { impl_->disable_idle_detection_ = true; }
+  virtual int CalculateSyncWaitTime(int last_wait, int user_idle_ms) {
+    return impl_->CalculateSyncWaitTime(last_wait, user_idle_ms);
+  }
+  virtual int CalculatePollingWaitTime(
+      const AllStatus::Status& status,
+      int last_poll_wait,  // in s
+      int* user_idle_milliseconds,
+      bool* continue_sync_cycle) {
+    return impl_->CalculatePollingWaitTime(status, last_poll_wait,
+        user_idle_milliseconds, continue_sync_cycle);
+  }
+ private:
+  scoped_ptr<SyncerThreadPthreadImpl> impl_;
+  DISALLOW_COPY_AND_ASSIGN(SyncerThreadPthreads);
+};
+
+}  // namespace browser_sync
+
+#endif  // CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_PTHREADS_H_
\ No newline at end of file
diff --git a/chrome/browser/sync/engine/syncer_thread_timed_stop.cc b/chrome/browser/sync/engine/syncer_thread_timed_stop.cc
new file mode 100644
index 0000000..a396dd0
--- /dev/null
+++ b/chrome/browser/sync/engine/syncer_thread_timed_stop.cc
@@ -0,0 +1,119 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#include "chrome/browser/sync/engine/syncer_thread_timed_stop.h"
+
+#include "build/build_config.h"
+
+#ifdef OS_MACOSX
+#include <CoreFoundation/CFNumber.h>
+#include <IOKit/IOTypes.h>
+#include <IOKit/IOKitLib.h>
+#endif
+
+#include <algorithm>
+#include <map>
+#include <queue>
+
+#include "chrome/browser/sync/engine/auth_watcher.h"
+#include "chrome/browser/sync/engine/model_safe_worker.h"
+#include "chrome/browser/sync/engine/net/server_connection_manager.h"
+#include "chrome/browser/sync/engine/syncer.h"
+#include "chrome/browser/sync/notifier/listener/talk_mediator.h"
+#include "chrome/browser/sync/notifier/listener/talk_mediator_impl.h"
+#include "chrome/browser/sync/syncable/directory_manager.h"
+
+using std::priority_queue;
+using std::min;
+using base::Time;
+using base::TimeDelta;
+using base::TimeTicks;
+
+namespace browser_sync {
+
+SyncerThreadTimedStop::SyncerThreadTimedStop(
+    ClientCommandChannel* command_channel,
+    syncable::DirectoryManager* mgr,
+    ServerConnectionManager* connection_manager,
+    AllStatus* all_status,
+    ModelSafeWorker* model_safe_worker)
+    : SyncerThread(command_channel, mgr, connection_manager, all_status,
+                   model_safe_worker),
+      in_thread_main_loop_(false) {
+}
+
+// Stop processing. A max wait of at least 2*server RTT time is recommended.
+// Returns true if we stopped, false otherwise.
+bool SyncerThreadTimedStop::Stop(int max_wait) {
+  AutoLock lock(lock_);
+  // If the thread has been started, then we either already have or are about to
+  // enter ThreadMainLoop so we have to proceed with shutdown and wait for it to
+  // finish.  If the thread has not been started --and we now own the lock--
+  // then we can early out because the caller has not called Start().
+  if (!thread_.IsRunning())
+    return true;
+
+  LOG(INFO) << "SyncerThread::Stop - setting ThreadMain exit condition to "
+    << "true (vault_.stop_syncer_thread_)";
+  // Exit the ThreadMainLoop once the syncer finishes (we tell it to exit
+  // below).
+  vault_.stop_syncer_thread_ = true;
+  if (NULL != vault_.syncer_) {
+    // Try to early exit the syncer.
+    vault_.syncer_->RequestEarlyExit();
+  }
+
+  // stop_syncer_thread_ is now true and the Syncer has been told to exit.
+  // We want to wake up all waiters so they can re-examine state. We signal,
+  // causing all waiters to try to re-acquire the lock, and then we atomically
+  // release the lock and wait.  Our wait can be spuriously signaled, so we
+  // recalculate the remaining sleep time each time through and re-
+  // check the condition before exiting the loop.
+  vault_field_changed_.Broadcast();
+  TimeTicks start = TimeTicks::Now();
+  TimeTicks end = start + TimeDelta::FromMilliseconds(max_wait);
+  bool timed_out = false;
+  // Eventually the combination of RequestEarlyExit and setting
+  // stop_syncer_thread_ to true above will cause in_thread_main_loop_ to become
+  // false.
+  while (in_thread_main_loop_) {
+    TimeDelta sleep_time = end - TimeTicks::Now();
+    if (sleep_time < TimeDelta::FromSeconds(0)) {
+      timed_out = true;
+      break;
+    }
+    LOG(INFO) << "Waiting in stop for " << sleep_time.InSeconds() << "s.";
+    vault_field_changed_.TimedWait(sleep_time);
+  }
+
+  if (timed_out) {
+    LOG(ERROR) << "SyncerThread::Stop timed out or error. Problems likely.";
+    return false;
+  }
+
+  // Stop() should not block on anything at this point, given above madness.
+  DLOG(INFO) << "Calling SyncerThread::thread_.Stop() at "
+             << Time::Now().ToInternalValue();
+  thread_.Stop();
+  DLOG(INFO) << "SyncerThread::thread_.Stop() finished at "
+             << Time::Now().ToInternalValue();
+  return true;
+}
+
+void SyncerThreadTimedStop::ThreadMain() {
+  AutoLock lock(lock_);
+  // Signal Start() to let it know we've made it safely are now running on the
+  // message loop, and unblock it's caller.
+  thread_main_started_.Signal();
+
+  // The only thing that could be waiting on this value is Stop, and we don't
+  // release the lock until we're far enough along to Stop safely.
+  in_thread_main_loop_ = true;
+  vault_field_changed_.Broadcast();
+  ThreadMainLoop();
+  in_thread_main_loop_ = false;
+  vault_field_changed_.Broadcast();
+  LOG(INFO) << "Syncer thread ThreadMain is done.";
+}
+
+}  // namespace browser_sync
\ No newline at end of file
diff --git a/chrome/browser/sync/engine/syncer_thread_timed_stop.h b/chrome/browser/sync/engine/syncer_thread_timed_stop.h
new file mode 100644
index 0000000..e1037a1
--- /dev/null
+++ b/chrome/browser/sync/engine/syncer_thread_timed_stop.h
@@ -0,0 +1,53 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// A class to run the syncer on a thread.  This guy is the closest chrome-based
+// (as opposed to pthreads based) SyncerThread to the old pthread implementation
+// in semantics, as it supports a timeout on Stop() -- It is just an override of
+// two methods from SyncerThread: ThreadMain and Stop -- to provide this.
+#ifndef CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_TIMED_STOP_H_
+#define CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_TIMED_STOP_H_
+
+#include <list>
+#include <map>
+#include <queue>
+#include <vector>
+
+#include "chrome/browser/sync/engine/syncer_thread.h"
+
+namespace browser_sync {
+
+class SyncerThreadTimedStop : public SyncerThread {
+  FRIEND_TEST(SyncerThreadTest, CalculateSyncWaitTime);
+  FRIEND_TEST(SyncerThreadTest, CalculatePollingWaitTime);
+  FRIEND_TEST(SyncerThreadWithSyncerTest, Polling);
+  FRIEND_TEST(SyncerThreadWithSyncerTest, Nudge);
+  friend class SyncerThreadWithSyncerTest;
+  friend class SyncerThreadFactory;
+ public:
+  virtual ~SyncerThreadTimedStop() {}
+
+  // Stop processing.  This version comes with a supported max_wait.
+  // A max wait of at least 2*server RTT time is recommended.
+  // Returns true if we stopped, false otherwise.
+  virtual bool Stop(int max_wait);
+
+ private:
+  SyncerThreadTimedStop(ClientCommandChannel* command_channel,
+      syncable::DirectoryManager* mgr,
+      ServerConnectionManager* connection_manager, AllStatus* all_status,
+      ModelSafeWorker* model_safe_worker);
+  virtual void ThreadMain();
+
+  // We use this to track when our synthesized thread loop is active, so we can
+  // timed-wait for it to become false.  For this and only this (temporary)
+  // implementation, we protect this variable using our parent lock_.
+  bool in_thread_main_loop_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncerThreadTimedStop);
+};
+
+}  // namespace browser_sync
+
+#endif  // CHROME_BROWSER_SYNC_ENGINE_SYNCER_THREAD_TIMED_STOP_H_
\ No newline at end of file
diff --git a/chrome/browser/sync/engine/syncer_thread_unittest.cc b/chrome/browser/sync/engine/syncer_thread_unittest.cc
index 6b758a7..fa28f7f 100644
--- a/chrome/browser/sync/engine/syncer_thread_unittest.cc
+++ b/chrome/browser/sync/engine/syncer_thread_unittest.cc
@@ -7,89 +7,158 @@
 #include <set>
 #include <strstream>
 
+#include "base/command_line.h"
 #include "base/scoped_ptr.h"
+#include "base/time.h"
+#include "chrome/browser/sync/engine/model_safe_worker.h"
 #include "chrome/browser/sync/engine/syncer_thread.h"
+#include "chrome/browser/sync/engine/syncer_thread_timed_stop.h"
+#include "chrome/test/sync/engine/mock_server_connection.h"
+#include "chrome/test/sync/engine/test_directory_setter_upper.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using base::Time;
+using base::TimeDelta;
+
 namespace browser_sync {
 
-class SyncerThreadTest : public testing::Test {
- protected:
-  SyncerThreadTest() {}
-  virtual ~SyncerThreadTest() {}
-  virtual void SetUp() {}
-  virtual void TearDown() {}
+typedef testing::Test SyncerThreadTest;
+
+class SyncerThreadWithSyncerTest : public testing::Test {
+ public:
+  SyncerThreadWithSyncerTest() {}
+  virtual void SetUp() {
+    metadb_.SetUp();
+    connection_.reset(new MockConnectionManager(metadb_.manager(),
+                                                metadb_.name()));
+    allstatus_.reset(new AllStatus());
+
+    syncer_thread_ = SyncerThreadFactory::Create(NULL, metadb_.manager(),
+        connection_.get(), allstatus_.get(), new ModelSafeWorker());
+
+    allstatus_->WatchSyncerThread(syncer_thread_);
+    syncer_thread_->SetConnected(true);
+  }
+  virtual void TearDown() {
+    syncer_thread_ = NULL;
+    allstatus_.reset();
+    connection_.reset();
+    metadb_.TearDown();
+  }
 
+  ManuallyOpenedTestDirectorySetterUpper* metadb() { return &metadb_; }
+  MockConnectionManager* connection() { return connection_.get(); }
+  SyncerThread* syncer_thread() { return syncer_thread_; }
+ private:
+  ManuallyOpenedTestDirectorySetterUpper metadb_;
+  scoped_ptr<MockConnectionManager> connection_;
+  scoped_ptr<AllStatus> allstatus_;
+  scoped_refptr<SyncerThread> syncer_thread_;
+  DISALLOW_COPY_AND_ASSIGN(SyncerThreadWithSyncerTest);
+};
+
+class SyncShareIntercept : public MockConnectionManager::MidCommitObserver {
+ public:
+  SyncShareIntercept() : sync_occured_(false, false) {}
+  virtual ~SyncShareIntercept() {}
+  virtual void Observe() {
+    times_sync_occured_.push_back(Time::NowFromSystemTime());
+    sync_occured_.Signal();
+  }
+  void WaitForSyncShare(int at_least_this_many, TimeDelta max_wait) {
+    while (at_least_this_many-- > 0)
+      sync_occured_.TimedWait(max_wait);
+  }
+  std::vector<Time> times_sync_occured() const {
+    return times_sync_occured_;
+  }
  private:
-  DISALLOW_COPY_AND_ASSIGN(SyncerThreadTest);
+  std::vector<Time> times_sync_occured_;
+  base::WaitableEvent sync_occured_;
+  DISALLOW_COPY_AND_ASSIGN(SyncShareIntercept);
 };
 
 TEST_F(SyncerThreadTest, Construction) {
-  SyncerThread syncer_thread(NULL, NULL, NULL, NULL, NULL);
+  scoped_refptr<SyncerThread> syncer_thread(
+      SyncerThreadFactory::Create(NULL, NULL, NULL, NULL, NULL));
+}
+
+TEST_F(SyncerThreadTest, StartStop) {
+  scoped_refptr<SyncerThread> syncer_thread(
+      SyncerThreadFactory::Create(NULL, NULL, NULL, NULL, NULL));
+  EXPECT_TRUE(syncer_thread->Start());
+  EXPECT_TRUE(syncer_thread->Stop(2000));
+
+  // Do it again for good measure.  I caught some bugs by adding this so
+  // I would recommend keeping it.
+  EXPECT_TRUE(syncer_thread->Start());
+  EXPECT_TRUE(syncer_thread->Stop(2000));
 }
 
 TEST_F(SyncerThreadTest, CalculateSyncWaitTime) {
-  SyncerThread syncer_thread(NULL, NULL, NULL, NULL, NULL);
-  syncer_thread.DisableIdleDetection();
+  scoped_refptr<SyncerThread> syncer_thread(
+      SyncerThreadFactory::Create(NULL, NULL, NULL, NULL, NULL));
+  syncer_thread->DisableIdleDetection();
+
+  // Syncer_polling_interval_ is less than max poll interval.
+  TimeDelta syncer_polling_interval = TimeDelta::FromSeconds(1);
 
-  // Syncer_polling_interval_ is less than max poll interval
-  int syncer_polling_interval = 1;  // Needed since AssertionResult is not a
-                                    // friend of SyncerThread
-  syncer_thread.syncer_polling_interval_ = syncer_polling_interval;
+  syncer_thread->SetSyncerPollingInterval(syncer_polling_interval);
 
   // user_idle_ms is less than 10 * (syncer_polling_interval*1000).
-  ASSERT_EQ(syncer_polling_interval * 1000,
-            syncer_thread.CalculateSyncWaitTime(1000, 0));
-  ASSERT_EQ(syncer_polling_interval * 1000,
-            syncer_thread.CalculateSyncWaitTime(1000, 1));
+  ASSERT_EQ(syncer_polling_interval.InMilliseconds(),
+            syncer_thread->CalculateSyncWaitTime(1000, 0));
+  ASSERT_EQ(syncer_polling_interval.InMilliseconds(),
+            syncer_thread->CalculateSyncWaitTime(1000, 1));
 
   // user_idle_ms is ge than 10 * (syncer_polling_interval*1000).
   int last_poll_time = 2000;
   ASSERT_LE(last_poll_time,
-            syncer_thread.CalculateSyncWaitTime(last_poll_time, 10000));
+            syncer_thread->CalculateSyncWaitTime(last_poll_time, 10000));
   ASSERT_GE(last_poll_time*3,
-            syncer_thread.CalculateSyncWaitTime(last_poll_time, 10000));
+            syncer_thread->CalculateSyncWaitTime(last_poll_time, 10000));
   ASSERT_LE(last_poll_time,
-            syncer_thread.CalculateSyncWaitTime(last_poll_time, 100000));
+            syncer_thread->CalculateSyncWaitTime(last_poll_time, 100000));
   ASSERT_GE(last_poll_time*3,
-            syncer_thread.CalculateSyncWaitTime(last_poll_time, 100000));
+            syncer_thread->CalculateSyncWaitTime(last_poll_time, 100000));
 
   // Maximum backoff time should be syncer_max_interval.
   int near_threshold = SyncerThread::kDefaultMaxPollIntervalMs / 2 - 1;
   int threshold = SyncerThread::kDefaultMaxPollIntervalMs;
   int over_threshold = SyncerThread::kDefaultMaxPollIntervalMs + 1;
   ASSERT_LE(near_threshold,
-            syncer_thread.CalculateSyncWaitTime(near_threshold, 10000));
+            syncer_thread->CalculateSyncWaitTime(near_threshold, 10000));
   ASSERT_GE(SyncerThread::kDefaultMaxPollIntervalMs,
-            syncer_thread.CalculateSyncWaitTime(near_threshold, 10000));
+            syncer_thread->CalculateSyncWaitTime(near_threshold, 10000));
   ASSERT_EQ(SyncerThread::kDefaultMaxPollIntervalMs,
-            syncer_thread.CalculateSyncWaitTime(threshold, 10000));
+            syncer_thread->CalculateSyncWaitTime(threshold, 10000));
   ASSERT_EQ(SyncerThread::kDefaultMaxPollIntervalMs,
-            syncer_thread.CalculateSyncWaitTime(over_threshold, 10000));
+            syncer_thread->CalculateSyncWaitTime(over_threshold, 10000));
 
   // Possible idle time must be capped by syncer_max_interval.
   int over_sync_max_interval =
       SyncerThread::kDefaultMaxPollIntervalMs + 1;
-  syncer_polling_interval = over_sync_max_interval / 100;  // so 1000* is right
-  syncer_thread.syncer_polling_interval_ = syncer_polling_interval;
-  ASSERT_EQ(syncer_polling_interval * 1000,
-            syncer_thread.CalculateSyncWaitTime(1000, over_sync_max_interval));
-  syncer_polling_interval = 1;
-  syncer_thread.syncer_polling_interval_ = syncer_polling_interval;
+  syncer_polling_interval = TimeDelta::FromSeconds(
+      over_sync_max_interval / 100);  // so 1000* is right
+  syncer_thread->SetSyncerPollingInterval(syncer_polling_interval);
+  ASSERT_EQ(syncer_polling_interval.InSeconds() * 1000,
+            syncer_thread->CalculateSyncWaitTime(1000, over_sync_max_interval));
+  syncer_polling_interval = TimeDelta::FromSeconds(1);
+  syncer_thread->SetSyncerPollingInterval(syncer_polling_interval);
   ASSERT_LE(last_poll_time,
-            syncer_thread.CalculateSyncWaitTime(last_poll_time,
+            syncer_thread->CalculateSyncWaitTime(last_poll_time,
                                                 over_sync_max_interval));
   ASSERT_GE(last_poll_time * 3,
-            syncer_thread.CalculateSyncWaitTime(last_poll_time,
+            syncer_thread->CalculateSyncWaitTime(last_poll_time,
                                                 over_sync_max_interval));
 }
 
 TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
   // Set up the environment.
   int user_idle_milliseconds_param = 0;
-
-  SyncerThread syncer_thread(NULL, NULL, NULL, NULL, NULL);
-  syncer_thread.DisableIdleDetection();
+  scoped_refptr<SyncerThread> syncer_thread(
+      SyncerThreadFactory::Create(NULL, NULL, NULL, NULL, NULL));
+  syncer_thread->DisableIdleDetection();
 
   // Notifications disabled should result in a polling interval of
   // kDefaultShortPollInterval.
@@ -100,7 +169,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
 
     // No work and no backoff.
     ASSERT_EQ(SyncerThread::kDefaultShortPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   0,
                   &user_idle_milliseconds_param,
@@ -110,7 +179,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     // In this case the continue_sync_cycle is turned off.
     continue_sync_cycle_param = true;
     ASSERT_EQ(SyncerThread::kDefaultShortPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   0,
                   &user_idle_milliseconds_param,
@@ -131,7 +200,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
 
     // No work and no backoff.
     ASSERT_EQ(SyncerThread::kDefaultLongPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   0,
                   &user_idle_milliseconds_param,
@@ -141,7 +210,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     // In this case the continue_sync_cycle is turned off.
     continue_sync_cycle_param = true;
     ASSERT_EQ(SyncerThread::kDefaultLongPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   0,
                   &user_idle_milliseconds_param,
@@ -162,7 +231,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     status.updates_received = 0;
     bool continue_sync_cycle_param = false;
 
-    ASSERT_LE(0, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_LE(0, syncer_thread->CalculatePollingWaitTime(
                      status,
                      0,
                      &user_idle_milliseconds_param,
@@ -170,19 +239,19 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     ASSERT_TRUE(continue_sync_cycle_param);
 
     continue_sync_cycle_param = false;
-    ASSERT_GE(3, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_GE(3, syncer_thread->CalculatePollingWaitTime(
                      status,
                      0,
                      &user_idle_milliseconds_param,
                      &continue_sync_cycle_param));
     ASSERT_TRUE(continue_sync_cycle_param);
 
-    ASSERT_LE(0, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_LE(0, syncer_thread->CalculatePollingWaitTime(
                      status,
                      0,
                      &user_idle_milliseconds_param,
                      &continue_sync_cycle_param));
-    ASSERT_GE(2, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_GE(2, syncer_thread->CalculatePollingWaitTime(
                      status,
                      0,
                      &user_idle_milliseconds_param,
@@ -191,7 +260,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
 
     status.updates_received = 1;
     ASSERT_EQ(SyncerThread::kDefaultShortPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   10,
                   &user_idle_milliseconds_param,
@@ -204,7 +273,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     status.unsynced_count = 1;
     bool continue_sync_cycle_param = false;
 
-    ASSERT_LE(0, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_LE(0, syncer_thread->CalculatePollingWaitTime(
                      status,
                      0,
                      &user_idle_milliseconds_param,
@@ -212,7 +281,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     ASSERT_TRUE(continue_sync_cycle_param);
 
     continue_sync_cycle_param = false;
-    ASSERT_GE(2, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_GE(2, syncer_thread->CalculatePollingWaitTime(
                      status,
                      0,
                      &user_idle_milliseconds_param,
@@ -221,7 +290,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
 
     status.unsynced_count = 0;
     ASSERT_EQ(SyncerThread::kDefaultShortPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   4,
                   &user_idle_milliseconds_param,
@@ -237,7 +306,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
 
     // Expect move from default polling interval to exponential backoff due to
     // unsynced_count != 0.
-    ASSERT_LE(0, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_LE(0, syncer_thread->CalculatePollingWaitTime(
                      status,
                      3600,
                      &user_idle_milliseconds_param,
@@ -245,7 +314,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     ASSERT_TRUE(continue_sync_cycle_param);
 
     continue_sync_cycle_param = false;
-    ASSERT_GE(2, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_GE(2, syncer_thread->CalculatePollingWaitTime(
                      status,
                      3600,
                      &user_idle_milliseconds_param,
@@ -253,12 +322,12 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     ASSERT_TRUE(continue_sync_cycle_param);
 
     // Expect exponential backoff.
-    ASSERT_LE(2, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_LE(2, syncer_thread->CalculatePollingWaitTime(
                      status,
                      2,
                      &user_idle_milliseconds_param,
                      &continue_sync_cycle_param));
-    ASSERT_GE(6, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_GE(6, syncer_thread->CalculatePollingWaitTime(
                      status,
                      2,
                      &user_idle_milliseconds_param,
@@ -268,7 +337,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     // A nudge resets the continue_sync_cycle_param value, so our backoff
     // should return to the minimum.
     continue_sync_cycle_param = false;
-    ASSERT_LE(0, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_LE(0, syncer_thread->CalculatePollingWaitTime(
                      status,
                      3600,
                      &user_idle_milliseconds_param,
@@ -276,7 +345,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     ASSERT_TRUE(continue_sync_cycle_param);
 
     continue_sync_cycle_param = false;
-    ASSERT_GE(2, syncer_thread.CalculatePollingWaitTime(
+    ASSERT_GE(2, syncer_thread->CalculatePollingWaitTime(
                      status,
                      3600,
                      &user_idle_milliseconds_param,
@@ -286,7 +355,7 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
     // Setting unsynced_count = 0 returns us to the default polling interval.
     status.unsynced_count = 0;
     ASSERT_EQ(SyncerThread::kDefaultShortPollIntervalSeconds,
-              syncer_thread.CalculatePollingWaitTime(
+              syncer_thread->CalculatePollingWaitTime(
                   status,
                   4,
                   &user_idle_milliseconds_param,
@@ -295,4 +364,67 @@ TEST_F(SyncerThreadTest, CalculatePollingWaitTime) {
   }
 }
 
+TEST_F(SyncerThreadWithSyncerTest, Polling) {
+  SyncShareIntercept interceptor;
+  connection()->SetMidCommitObserver(&interceptor);
+
+  const TimeDelta poll_interval = TimeDelta::FromSeconds(1);
+  syncer_thread()->SetSyncerShortPollInterval(poll_interval);
+  EXPECT_TRUE(syncer_thread()->Start());
+
+  // Calling Open() should cause the SyncerThread to create a Syncer.
+  metadb()->Open();
+
+  TimeDelta two_polls = poll_interval + poll_interval;
+  // We could theoretically return immediately from the wait if the interceptor
+  // was already signaled for a SyncShare (the first one comes quick).
+  interceptor.WaitForSyncShare(1, two_polls);
+  EXPECT_FALSE(interceptor.times_sync_occured().empty());
+
+  // Wait for at least 2 more SyncShare operations.
+  interceptor.WaitForSyncShare(2, two_polls);
+  EXPECT_TRUE(syncer_thread()->Stop(2000));
+
+  // Now analyze the run.
+  std::vector<Time> data = interceptor.times_sync_occured();
+
+  EXPECT_GE(data.size(), static_cast<unsigned int>(3));
+  for (unsigned int i = 0; i < data.size() - 1; i++) {
+    Time optimal_next_sync = data[i] + poll_interval;
+    // The pthreads impl uses a different time impl and is slightly (~900usecs)
+    // off, so this expectation can fail with --syncer-thread-pthreads.
+    EXPECT_TRUE(data[i + 1] >= optimal_next_sync)
+        << "difference is "
+        << (data[i + 1] - optimal_next_sync).InMicroseconds() << " usecs. "
+        << "~900usec delta is OK with --syncer-thread-pthreads";
+    // This should be reliable, as there are no blocking or I/O operations
+    // except the explicit 2 second wait, so if it takes longer than this
+    // there is a problem.
+    EXPECT_TRUE(data[i + 1] < optimal_next_sync + poll_interval);
+  }
+}
+
+TEST_F(SyncerThreadWithSyncerTest, Nudge) {
+  SyncShareIntercept interceptor;
+  connection()->SetMidCommitObserver(&interceptor);
+  // We don't want a poll to happen during this test (except the first one).
+  const TimeDelta poll_interval = TimeDelta::FromMinutes(5);
+  syncer_thread()->SetSyncerShortPollInterval(poll_interval);
+  EXPECT_TRUE(syncer_thread()->Start());
+  metadb()->Open();
+  interceptor.WaitForSyncShare(1, poll_interval + poll_interval);
+
+  EXPECT_EQ(static_cast<unsigned int>(1),
+            interceptor.times_sync_occured().size());
+  // The SyncerThread should be waiting for the poll now.  Nudge it to sync
+  // immediately (5ms).
+  syncer_thread()->NudgeSyncer(5, SyncerThread::kUnknown);
+  interceptor.WaitForSyncShare(1, TimeDelta::FromSeconds(1));
+  EXPECT_EQ(static_cast<unsigned int>(2),
+      interceptor.times_sync_occured().size());
+
+  // SyncerThread should be waiting again.  Signal it to stop.
+  EXPECT_TRUE(syncer_thread()->Stop(2000));
+}
+
 }  // namespace browser_sync