sync: Add non-blocking type encryption support

sync/engine/entity_tracker.cc

 // Copyright 2014 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 "sync/engine/entity_tracker.h"
 
 #include "base/logging.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/non_blocking_sync_common.h"
 #include "sync/syncable/syncable_util.h"
@@ skipping 175 matching lines @@
   highest_commit_response_version_ = response_version;
 
   // Because an in-progress commit blocks the sync thread, we can assume that
   // the item we just committed successfully is exactly the one we have now.
   // Nothing changed it while the commit was happening.  Since we're now in
   // sync with the server, we can clear the pending commit.
   ClearPendingCommit();
 }
 
 void EntityTracker::ReceiveUpdate(int64 version) {
-  highest_gu_response_version_ =
-      std::max(highest_gu_response_version_, 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();
 
   if (IsInConflict()) {
     // Incoming update clobbers the pending commit on the sync thread.
     // The model thread can re-request this commit later if it wants to.
     ClearPendingCommit();
   }
 }
 
+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
     // client.  We're fully up to date, and therefore not in conflict.
     return false;
   } else {
     // The most recent server state was written by someone else.
     // Did the model thread have the most up to date version when it issued the
     // commit request?
     if (base_version_ >= highest_gu_response_version_) {
       return false;  // Yes.
     } else {
       return true;  // No.
     }
   }
 }
 
 bool EntityTracker::IsServerKnown() const {
   return base_version_ != kUncommittedVersion;
 }
 
 void EntityTracker::ClearPendingCommit() {
   is_commit_pending_ = false;
 
   // Clearing the specifics might free up some memory.  It can't hurt to try.
   specifics_.Clear();
 }
 
 }  // namespace syncer