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

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

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/bookmarks/bookmark_name_folder_controller.h"
 
 #include "base/mac/mac_util.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/cocoa/bookmarks/bookmark_model_observer_for_cocoa.h"
 #include "grit/generated_resources.h"
 #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).
 - (id)initWithParentWindow:(NSWindow*)window
                    profile:(Profile*)profile
                       node:(const BookmarkNode*)node
                     parent:(const BookmarkNode*)parent
                   newIndex:(int)newIndex {
   NSString* nibpath = [base::mac::MainAppBundle()
                         pathForResource:@"BookmarkNameFolder"
@@ skipping 36 matching lines @@
   DCHECK(parent);
   return [self initWithParentWindow:window
                             profile:profile
                                node:nil
                              parent:parent
                            newIndex:newIndex];
 }
 
 - (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 {
   // Ping me when things change out from under us.
   observer_.reset(new BookmarkModelObserverForCocoa(
                     node_, profile_->GetBookmarkModel(),
                     self,
                     @selector(cancel:)));
   [NSApp beginSheet:[self window]
      modalForWindow:parentWindow_
@@ skipping 33 matching lines @@
 
 - (void)setFolderName:(NSString*)name {
   [nameField_ setStringValue:name];
 }
 
 - (NSButton*)okButton {
   return okButton_;
 }
 
 @end  // BookmarkNameFolderController