Add shutdown notification and service refs to SyncServiceObserver.

chrome/browser/ui/webui/options/clear_browser_data_handler.cc

Index: chrome/browser/ui/webui/options/clear_browser_data_handler.cc
diff --git a/chrome/browser/ui/webui/options/clear_browser_data_handler.cc b/chrome/browser/ui/webui/options/clear_browser_data_handler.cc
index 0d7767128d979c0671e706dc878005b1a2bc1c33..caddf9d8e11b89d019a0d6d2f8ce37f55bfceb0d 100644
--- a/chrome/browser/ui/webui/options/clear_browser_data_handler.cc
+++ b/chrome/browser/ui/webui/options/clear_browser_data_handler.cc
@@ -391,7 +391,7 @@ void ClearBrowserDataHandler::UpdateCounterText(
       base::StringValue(GetChromeCounterTextFromResult(result.get())));
 }
 
-void ClearBrowserDataHandler::OnStateChanged() {
+void ClearBrowserDataHandler::OnStateChanged(syncer::SyncService* sync) {
   web_ui()->CallJavascriptFunctionUnsafe(
       "ClearBrowserDataOverlay.updateSyncWarningAndHistoryFooter",
       base::FundamentalValue(sync_service_ && sync_service_->IsSyncActive()),
@@ -423,7 +423,7 @@ void ClearBrowserDataHandler::RefreshHistoryNotice() {
 
 void ClearBrowserDataHandler::UpdateHistoryNotice(bool show) {
   should_show_history_notice_ = show;
-  OnStateChanged();
+  OnStateChanged(nullptr);

[sky, 2017/01/27 16:29:44]

This seems error prone. I recommend having OnStateChanged() and this call a
function with no args. Maybe UpdateSyncState() as other files have.

[Steven Holte, 2017/01/27 20:11:45]

Done.

 
   UMA_HISTOGRAM_BOOLEAN(
       "History.ClearBrowsingData.HistoryNoticeShownInFooterWhenUpdated",