Move BrowserThread to content namespace.

content/browser/renderer_host/clipboard_message_filter_mac.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.
 
 #include "content/browser/renderer_host/clipboard_message_filter.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/sys_string_conversions.h"
 #import "content/browser/find_pasteboard.h"
 #include "content/public/browser/browser_thread.h"
 
+using content::BrowserThread;
+
 // The number of utf16 code units that will be written to the find pasteboard,
 // longer texts are silently ignored. This is to prevent that a compromised
 // renderer can write unlimited amounts of data into the find pasteboard.
 static const size_t kMaxFindPboardStringLength = 4096;
 
 class WriteFindPboardTask : public Task {
  public:
   explicit WriteFindPboardTask(NSString* text)
       : text_([text retain]) {}
 
   void Run() {
     [[FindPasteboard sharedInstance] setFindText:text_];
   }
 
  private:
   scoped_nsobject<NSString> text_;
 };
 
 // Called on the IO thread.
 void ClipboardMessageFilter::OnFindPboardWriteString(const string16& text) {
   if (text.length() <= kMaxFindPboardStringLength) {
     NSString* nsText = base::SysUTF16ToNSString(text);
     if (nsText) {
       // FindPasteboard must be used on the UI thread.
       BrowserThread::PostTask(
           BrowserThread::UI, FROM_HERE, new WriteFindPboardTask(nsText));
     }
   }
 }