[Sync] Fix flakiness from Sessions refactor

components/sync_sessions/synced_session_tracker.cc

Index: components/sync_sessions/synced_session_tracker.cc
diff --git a/components/sync_sessions/synced_session_tracker.cc b/components/sync_sessions/synced_session_tracker.cc
index e797295ba70b1fea02aa303affb936a3abcd4f6f..67c075c8b3ca6edc5672728894340826e1e1586b 100644
--- a/components/sync_sessions/synced_session_tracker.cc
+++ b/components/sync_sessions/synced_session_tracker.cc
@@ -261,7 +261,11 @@ void SyncedSessionTracker::PutTabInWindow(const std::string& session_tag,
     tab = std::move(it->second);
     unmapped_tabs_[session_tag].erase(it);
   }
-  DCHECK(tab);
+  if (!tab) {
+    LOG(ERROR) << "crbug.com/665196 Attempting to map tab " << tab_id

[skym, 2016/12/09 15:40:00]

This doesn't seem like the right bug number.

[Nicolas Zea, 2016/12/09 17:33:36]

Oops! Fixed

+               << " multiple times!";
+    return;
+  }
 
   tab->window_id.set_id(window_id);
   DVLOG(1) << "  - tab " << tab_id << " added to window " << window_id;