[Mac] Workaround for Mavericks AppKit accessibility bug in NSCollectionView.

ui/app_list/cocoa/apps_grid_view_item.mm

Index: ui/app_list/cocoa/apps_grid_view_item.mm
diff --git a/ui/app_list/cocoa/apps_grid_view_item.mm b/ui/app_list/cocoa/apps_grid_view_item.mm
index ccd6b80db84dbb2cca426fd44ebc0149c95f638d..08304da155cadd2551730eaf333caf7773afc9a6 100644
--- a/ui/app_list/cocoa/apps_grid_view_item.mm
+++ b/ui/app_list/cocoa/apps_grid_view_item.mm
@@ -458,4 +458,11 @@ void ItemModelObserverBridge::ItemPercentDownloadedChanged() {
             inView:controlView];
 }
 
+// Workaround for http://crbug.com/324365: AppKit in Mavericks tries to call
+// - [NSButtonCell item] when inspecting accessibility. Without this, an
+// unrecognized selector exception is thrown inside AppKit, crashing Chrome.
+- (id)item {
+  return nil;
+}
+
 @end