Disable ui::Clipboard on the FILE thread.

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 70e5627c9c54af4e3ef414f62058feacb4189859..f46aedae2000dcf5f1cf1f4f04e33f6404063067 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -1374,8 +1374,7 @@ int BrowserMainLoop::BrowserThreadsStarted() {
   // The current thread is the UI thread.
   allowed_clipboard_threads.push_back(base::PlatformThread::CurrentId());
 #if defined(OS_WIN)
-  // On Windows, clipboards are also used on the FILE or IO threads.
-  allowed_clipboard_threads.push_back(file_thread_->GetThreadId());
+  // On Windows, clipboard is also used on the IO thread.
   allowed_clipboard_threads.push_back(io_thread_->GetThreadId());
 #endif
   ui::Clipboard::SetAllowedThreads(allowed_clipboard_threads);