mash: Update shelf pin prefs in ShelfModelObserver overrides.

chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
index 51355bcb57bd5dd6c755898c4e0fdd582bf3b799..815b0fb06ee6b9887848a0ebd16ea7125ceffe40 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
@@ -5,7 +5,6 @@
 #include "chrome/browser/ui/ash/launcher/chrome_launcher_controller.h"
 
 #include "ash/public/interfaces/constants.mojom.h"
-#include "base/auto_reset.h"
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/chromeos/arc/arc_util.h"
 #include "chrome/browser/extensions/extension_app_icon_loader.h"
@@ -102,6 +101,14 @@ void ChromeLauncherController::SetShelfBehaviorsFromPrefs() {
   SetShelfAlignmentFromPrefs();
 }
 
+std::unique_ptr<base::AutoReset<bool>>
+ChromeLauncherController::DoNotSyncPinChanges() {
+  // Only one temporary block should not exist at a time.
+  DCHECK(should_sync_pin_changes_);
+  return base::MakeUnique<base::AutoReset<bool>>(&should_sync_pin_changes_,
+                                                 false);
+}
+
 void ChromeLauncherController::SetLauncherControllerHelperForTest(
     std::unique_ptr<LauncherControllerHelper> helper) {
   launcher_controller_helper_ = std::move(helper);