Make the PrintDlgEx() call in the UI thread.

chrome/common/temp_scaffolding_stubs.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_COMMON_TEMP_SCAFFOLDING_STUBS_H_
 #define CHROME_COMMON_TEMP_SCAFFOLDING_STUBS_H_
 
 // This file provides declarations and stub definitions for classes we encouter
 // during the porting effort. It is not meant to be permanent, and classes will
 // be removed from here as they are fleshed out more completely.
@@ skipping 126 matching lines @@
   void RenderParams(ViewMsg_Print_Params* params) const { NOTIMPLEMENTED(); }
   int dpi() const { NOTIMPLEMENTED(); return 92; }
 };
 
 class PrinterQuery : public base::RefCountedThreadSafe<PrinterQuery> {
  public:
   enum GetSettingsAskParam {
     DEFAULTS,
     ASK_USER,
   };
-
+  PrinterQuery(MessageLoop*) {}
   void GetSettings(GetSettingsAskParam ask_user_for_settings,
                    int parent_window,
                    int expected_page_count,
                    CancelableTask* callback) { NOTIMPLEMENTED(); }
   PrintingContext::Result last_status() { return PrintingContext::FAILED; }
   const PrintSettings& settings() { NOTIMPLEMENTED(); return settings_; }
   int cookie() { NOTIMPLEMENTED(); return 0; }
   void StopWorker() { NOTIMPLEMENTED(); }
 
  private:
@@ skipping 405 matching lines @@
   void InitHidden() { NOTIMPLEMENTED(); }
   void set_preferred_size(const gfx::Size& size) { NOTIMPLEMENTED(); }
   virtual void SetVisible(bool flag) { NOTIMPLEMENTED(); }
   void SizeToPreferredSize() { NOTIMPLEMENTED(); }
   HWNDHtmlView* GetParent() const { NOTIMPLEMENTED(); return NULL; }
   void Layout() { NOTIMPLEMENTED(); }
   void SchedulePaint() { NOTIMPLEMENTED(); }
 };
 
 #endif  // CHROME_COMMON_TEMP_SCAFFOLDING_STUBS_H_