Remove 10.5 support code.

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

 // Copyright (c) 2012 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_bubble_controller.h"
 
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
@@ skipping 47 matching lines @@
     model_ = model;
     node_ = node;
     alreadyBookmarked_ = alreadyBookmarked;
   }
   return self;
 }
 
 - (void)awakeFromNib {
   [super awakeFromNib];
 
-  // Check if NSTextFieldCell supports the method. This check is in place as
-  // only 10.6 and greater support the setUsesSingleLineMode method.
-  // TODO(kushi.p): Remove this when the project hits a 10.6+ only state.
-  NSTextFieldCell* nameFieldCell_ = [nameTextField_ cell];
-  if ([nameFieldCell_
-          respondsToSelector:@selector(setUsesSingleLineMode:)]) {
-    [nameFieldCell_ setUsesSingleLineMode:YES];
-  }
+  [[nameTextField_ cell] setUsesSingleLineMode:YES];
 }
 
 // If this is a new bookmark somewhere visible (e.g. on the bookmark
 // bar), pulse it.  Else, call ourself recursively with our parent
 // until we find something visible to pulse.
 - (void)startPulsingBookmarkButton:(const BookmarkNode*)node  {
   while (node) {
     if ((node->parent() == model_->bookmark_bar_node()) ||
         (node == model_->other_node())) {
       pulsingBookmarkNode_ = node;
@@ skipping 273 matching lines @@
   NSInteger idx = [menu indexOfItemWithRepresentedObject:parentValue];
   DCHECK(idx != -1);
   [folderPopUpButton_ selectItemAtIndex:idx];
 }
 
 - (NSPopUpButton*)folderPopUpButton {
   return folderPopUpButton_;
 }
 
 @end  // implementation BookmarkBubbleController(ExposedForUnitTesting)