Try 2 - Change how ui::Clipboard is accessed so there's only one per thread.

content/browser/browser_main_loop.cc

 // 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.
 
 #include "content/browser/browser_main_loop.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/hi_res_timer_manager.h"
@@ skipping 28 matching lines @@
 #include "content/public/browser/render_process_host.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "content/public/common/result_codes.h"
 #include "crypto/nss_util.h"
 #include "media/audio/audio_manager.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/ssl_config_service.h"
 #include "net/socket/client_socket_factory.h"
 #include "net/socket/tcp_client_socket.h"
+#include "ui/base/clipboard/clipboard.h"
 
 #if defined(USE_AURA)
 #include "content/browser/renderer_host/image_transport_factory.h"
 #endif
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <commctrl.h>
 #include <shellapi.h>
 
@@ skipping 170 matching lines @@
 BrowserMainLoop::BrowserMainLoop(const content::MainFunctionParams& parameters)
     : parameters_(parameters),
       parsed_command_line_(parameters.command_line),
       result_code_(content::RESULT_CODE_NORMAL_EXIT) {
   DCHECK(!g_current_browser_main_loop);
   g_current_browser_main_loop = this;
 }
 
 BrowserMainLoop::~BrowserMainLoop() {
   DCHECK_EQ(this, g_current_browser_main_loop);
+  ui::Clipboard::DestroyClipboardForCurrentThread();
   g_current_browser_main_loop = NULL;
 }
 
 void BrowserMainLoop::Init() {
   parts_.reset(
       GetContentClient()->browser()->CreateBrowserMainParts(parameters_));
 }
 
 // BrowserMainLoop stages ==================================================
 
@@ skipping 409 matching lines @@
   resource_dispatcher_host_.reset(new ResourceDispatcherHostImpl());
 
   // Start the GpuDataManager before we set up the MessageLoops because
   // otherwise we'll trigger the assertion about doing IO on the UI thread.
   content::GpuDataManager::GetInstance();
 #endif  // !OS_IOS
 
 #if defined(ENABLE_INPUT_SPEECH)
   speech_recognition_manager_.reset(new speech::SpeechRecognitionManagerImpl());
 #endif
+
+  // Alert the clipboard class to which threads are allowed to access the
+  // clipboard:
+  std::vector<base::PlatformThreadId> allowed_clipboard_threads;
+  // 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_->thread_id());
+  allowed_clipboard_threads.push_back(io_thread_->thread_id());
+#endif
+  ui::Clipboard::SetAllowedThreads(allowed_clipboard_threads);
 }
 
 void BrowserMainLoop::InitializeToolkit() {
   // TODO(evan): this function is rather subtle, due to the variety
   // of intersecting ifdefs we have.  To keep it easy to follow, there
   // are no #else branches on any #ifs.
   // TODO(stevenjb): Move platform specific code into platform specific Parts
   // (Need to add InitializeToolkit stage to BrowserParts).
 #if defined(OS_LINUX) || defined(OS_OPENBSD)
   // Glib type system initialization. Needed at least for gconf,
@@ skipping 37 matching lines @@
   DCHECK_EQ(MessageLoop::TYPE_UI, MessageLoop::current()->type());
   if (parameters_.ui_task)
     MessageLoopForUI::current()->PostTask(FROM_HERE, *parameters_.ui_task);
 
   base::RunLoop run_loop;
   run_loop.Run();
 #endif
 }
 
 }  // namespace content