[Sync] Don't DCHECK if we can't find the window for a tab

chrome/browser/ui/sync/browser_synced_window_delegate.cc

 // Copyright (c) 2012 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/ui/sync/browser_synced_window_delegate.h"
 
 #include <set>
 
 #include "chrome/browser/sessions/session_id.h"
 #include "chrome/browser/ui/browser.h"
@@ skipping 29 matching lines @@
 
 BrowserSyncedWindowDelegate::~BrowserSyncedWindowDelegate() {}
 
 bool BrowserSyncedWindowDelegate::IsTabPinned(
     const browser_sync::SyncedTabDelegate* tab) const {
   for (int i = 0; i < browser_->tab_strip_model()->count(); i++) {
     browser_sync::SyncedTabDelegate* current = GetTabAt(i);
     if (tab == current)
       return browser_->tab_strip_model()->IsTabPinned(i);
   }
-  NOTREACHED();
+  // The window and tab are not always updated atomically, so it's possible
+  // one of the values was stale. We'll retry later, just ignore for now.
   return false;
 }
 
 browser_sync::SyncedTabDelegate* BrowserSyncedWindowDelegate::GetTabAt(
     int index) const {
   return TabContentsSyncedTabDelegate::FromWebContents(
       browser_->tab_strip_model()->GetWebContentsAt(index));
 }
 
 SessionID::id_type BrowserSyncedWindowDelegate::GetTabIdAt(int index) const {
@@ skipping 24 matching lines @@
   return browser_->is_type_tabbed();
 }
 
 bool BrowserSyncedWindowDelegate::IsTypePopup() const {
   return browser_->is_type_popup();
 }
 
 bool BrowserSyncedWindowDelegate::IsSessionRestoreInProgress() const {
   return false;
 }