Change other usages of .size() to .empty() when applicable.

chrome/browser/bookmarks/bookmark_pasteboard_helper_mac.mm

 // Copyright (c) 2010 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.
 
 #include "chrome/browser/bookmarks/bookmark_pasteboard_helper_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
@@ skipping 206 matching lines @@
   NSURL* url = [NSURL URLWithString:[urls objectAtIndex:0]];
   [url writeToPasteboard:pb];
   NSString* titleString = [titles objectAtIndex:0];
   [pb setString:titleString forType:kNSURLTitlePboardType];
 }
 
 void WriteToClipboardPrivate(
     const std::vector<BookmarkNodeData::Element>& elements,
     NSPasteboard* pb,
     FilePath::StringType profile_path) {
-  if (elements.empty()) {
+  if (elements.empty())
     return;
-  }
+
   NSArray* types = [NSArray arrayWithObjects:kBookmarkDictionaryListPboardType,
                                              kWebURLsWithTitlesPboardType,
                                              NSStringPboardType,
                                              NSURLPboardType,
                                              kNSURLTitlePboardType,
                                              kChromiumProfilePathPboardType,
                                              nil];
   [pb declareTypes:types owner:nil];
   [pb setString:base::SysUTF8ToNSString(profile_path)
         forType:kChromiumProfilePathPboardType];
@@ skipping 75 matching lines @@
   scoped_nsobject<BookmarkDragSource> source([[BookmarkDragSource alloc]
       initWithContentsView:tabView
                   dropData:elements
                    profile:profile
                 pasteboard:pb
          dragOperationMask:NSDragOperationEvery]);
   [source startDrag];
 }
 
 }  // namespace bookmark_pasteboard_helper_mac