Mac: Make ScopedTypeRef require explicit constructors

chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm

Index: chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
diff --git a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
index 880beebf1528c9f9e06a62e8c2b61098dacbe7bd..7fd1beb3d387d2208f3c6239b1250f1a806c8472 100644
--- a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
@@ -495,8 +495,8 @@ - (void)redraw {
 - (void)removeViewForAction:(ToolbarActionViewController*)action {
   // We're about to remove the button view from the container as well as from
   // |buttons_|, so make sure we retain a reference.
-  base::scoped_nsobject<BrowserActionButton> button =
-      [[self buttonForId:action->GetId()] retain];
+  base::scoped_nsobject<BrowserActionButton> button(
+      [[self buttonForId:action->GetId()] retain]);
 
   // Note: We remove the button from the view and the buttons list first because
   // destroying it (or calling -onRemoved) can cause redraws, and we don't want