Revert of sync: Add non-blocking type encryption support

sync/engine/entity_tracker.cc

Index: sync/engine/entity_tracker.cc
diff --git a/sync/engine/entity_tracker.cc b/sync/engine/entity_tracker.cc
index bad76f9932575f43300e7ea74cea38e9e3d4b6df..0f10906ab15c67fc253b0e24c2115d650c0ef4b0 100644
--- a/sync/engine/entity_tracker.cc
+++ b/sync/engine/entity_tracker.cc
@@ -193,14 +193,8 @@
 }
 
 void EntityTracker::ReceiveUpdate(int64 version) {
-  if (version <= highest_gu_response_version_)
-    return;
-
-  highest_gu_response_version_ = version;
-
-  // Got an applicable update newer than any pending updates.  It must be safe
-  // to discard the old pending update, if there was one.
-  ClearPendingUpdate();
+  highest_gu_response_version_ =
+      std::max(highest_gu_response_version_, version);
 
   if (IsInConflict()) {
     // Incoming update clobbers the pending commit on the sync thread.
@@ -209,34 +203,9 @@
   }
 }
 
-bool EntityTracker::ReceivePendingUpdate(const UpdateResponseData& data) {
-  if (data.response_version < highest_gu_response_version_)
-    return false;
-
-  highest_gu_response_version_ = data.response_version;
-  pending_update_.reset(new UpdateResponseData(data));
-  ClearPendingCommit();
-  return true;
-}
-
-bool EntityTracker::HasPendingUpdate() const {
-  return !!pending_update_;
-}
-
-UpdateResponseData EntityTracker::GetPendingUpdate() const {
-  return *pending_update_;
-}
-
-void EntityTracker::ClearPendingUpdate() {
-  pending_update_.reset();
-}
-
 bool EntityTracker::IsInConflict() const {
   if (!is_commit_pending_)
     return false;
-
-  if (HasPendingUpdate())
-    return true;
 
   if (highest_gu_response_version_ <= highest_commit_response_version_) {
     // The most recent server state was created in a commit made by this