Do not allow multiline input when naming bookmarks/folders on Mac

chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.mm

Index: chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.mm
diff --git a/chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.mm b/chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.mm
index a4c4d0c222bca1ade56be713297f1cdd178f6ea9..73f77886c56c7b4049f0ba793053b4c1a901a640 100644
--- a/chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.mm
+++ b/chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.mm
@@ -12,6 +12,10 @@
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
+@interface NSCell(multilinebookmarks)
+- (void)setUsesSingleLineMode:(BOOL)flag;
+@end
+
 @implementation BookmarkNameFolderController
 
 // Common initializer (private).
@@ -68,6 +72,14 @@
 
 - (void)awakeFromNib {
   [nameField_ setStringValue:initialName_.get()];
+
+  // Check if NSTextFieldCell supports the method. This check is in place as
+  // only 10.6 and greater support the setUsesSingleLineMode method.
+  NSTextFieldCell* nameFieldCell_ = [nameField_ cell];
+  if ([nameFieldCell_
+          respondsToSelector:@selector(setUsesSingleLineMode:)]) {
+    [nameFieldCell_ setUsesSingleLineMode:YES];
+  }
 }
 
 - (void)runAsModalSheet {