Cleanup: Fix some lint errors in chrome/browser/ui.

chrome/browser/ui/ash/multi_user/multi_user_warning_dialog.cc

Index: chrome/browser/ui/ash/multi_user/multi_user_warning_dialog.cc
diff --git a/chrome/browser/ui/ash/multi_user/multi_user_warning_dialog.cc b/chrome/browser/ui/ash/multi_user/multi_user_warning_dialog.cc
index 9d5b70037ba920a63806dc348bd7509b1def2edc..ba747f5bbfce5241a325be338f6f1a3121ee84aa 100644
--- a/chrome/browser/ui/ash/multi_user/multi_user_warning_dialog.cc
+++ b/chrome/browser/ui/ash/multi_user/multi_user_warning_dialog.cc
@@ -31,10 +31,10 @@ const int kTopInset = 10;
 // Dialog for multi-profiles teleport warning.
 class TeleportWarningView : public views::DialogDelegateView {
  public:
-  TeleportWarningView(base::Callback<void(bool)> on_accept);
+  explicit TeleportWarningView(const base::Callback<void(bool)>& on_accept);
   virtual ~TeleportWarningView();
 
-  static void ShowDialog(const base::Callback<void(bool)> on_accept);
+  static void ShowDialog(const base::Callback<void(bool)>& on_accept);
 
   // views::DialogDelegate overrides.
   virtual bool Accept() OVERRIDE;
@@ -58,7 +58,7 @@ class TeleportWarningView : public views::DialogDelegateView {
 // TeleportWarningView implementation.
 
 TeleportWarningView::TeleportWarningView(
-    const base::Callback<void(bool)> on_accept)
+    const base::Callback<void(bool)>& on_accept)
     : on_accept_(on_accept) {
 }
 
@@ -67,7 +67,7 @@ TeleportWarningView::~TeleportWarningView() {
 
 // static
 void TeleportWarningView::ShowDialog(
-    const base::Callback<void(bool)> on_accept) {
+    const base::Callback<void(bool)>& on_accept) {
   TeleportWarningView* dialog_view =
       new TeleportWarningView(on_accept);
   views::DialogDelegate::CreateDialogWidget(
@@ -156,7 +156,7 @@ void TeleportWarningView::InitDialog() {
 // Factory function.
 
 void ShowMultiprofilesWarningDialog(
-   const base::Callback<void(bool)> on_accept) {
+    const base::Callback<void(bool)>& on_accept) {
   TeleportWarningView::ShowDialog(on_accept);
 }