diff --git a/atom/browser/ui/cocoa/atom_scrubber_data_source.h b/atom/browser/ui/cocoa/atom_scrubber_data_source.h
index 5850e307698a..57ef1509096a 100644
--- a/atom/browser/ui/cocoa/atom_scrubber_data_source.h
+++ b/atom/browser/ui/cocoa/atom_scrubber_data_source.h
@@ -18,8 +18,8 @@
   std::vector<mate::PersistentDictionary> items_;
 }
 
-- (id)initWithItems:(std::vector<mate::PersistentDictionary>)items;
-- (void)setItems:(std::vector<mate::PersistentDictionary>)items;
+- (id)initWithItems:(const std::vector<mate::PersistentDictionary>&)items;
+- (void)setItems:(const std::vector<mate::PersistentDictionary>&)items;
 
 @end
 
diff --git a/atom/browser/ui/cocoa/atom_scrubber_data_source.mm b/atom/browser/ui/cocoa/atom_scrubber_data_source.mm
index b320d7a2c3f2..3c8bb6b932b4 100644
--- a/atom/browser/ui/cocoa/atom_scrubber_data_source.mm
+++ b/atom/browser/ui/cocoa/atom_scrubber_data_source.mm
@@ -13,18 +13,19 @@
 static NSString* const TextItemIdentifier = @"scrubber.text.item";
 static NSString* const ImageItemIdentifier = @"scrubber.image.item";
 
-- (id)initWithItems:(std::vector<mate::PersistentDictionary>)items {
+- (id)initWithItems:(const std::vector<mate::PersistentDictionary>&)items {
   if ((self = [super init])) {
     items_ = items;
   }
   return self;
 }
 
-- (NSInteger)numberOfItemsForScrubber:(NSScrubber *)theScrubber {
+- (NSInteger)numberOfItemsForScrubber:(NSScrubber*)theScrubber {
   return items_.size();
 }
 
-- (NSScrubberItemView *)scrubber:(NSScrubber *)scrubber viewForItemAtIndex:(NSInteger)index {
+- (NSScrubberItemView*)scrubber:(NSScrubber*)scrubber
+             viewForItemAtIndex:(NSInteger)index {
   mate::PersistentDictionary item = items_[index];
 
   NSScrubberItemView* itemView;
@@ -48,7 +49,7 @@ static NSString* const ImageItemIdentifier = @"scrubber.image.item";
   return itemView;
 }
 
-- (void)setItems:(std::vector<mate::PersistentDictionary>)items {
+- (void)setItems:(const std::vector<mate::PersistentDictionary>&)items {
   items_ = items;
 }