Should handle the events when no printer is detected on local machine...

chrome/common/render_messages.h

 // Copyright (c) 2006-2008 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_RENDER_MESSAGES_H_
 #define CHROME_COMMON_RENDER_MESSAGES_H_
 
 #include <string>
 #include <vector>
 #include <map>
@@ skipping 290 matching lines @@
   int document_cookie;
 
   // Warning: do not compare document_cookie.
   bool Equals(const ViewMsg_Print_Params& rhs) const {
     return printable_size == rhs.printable_size &&
            dpi == rhs.dpi &&
            min_shrink == rhs.min_shrink &&
            max_shrink == rhs.max_shrink &&
            desired_dpi == rhs.desired_dpi;
   }
+
+  // Checking if the current params is empty. Just initialized after a memset.
+  bool IsEmpty() const {
+    return !document_cookie && !desired_dpi && !max_shrink && !min_shrink &&
+           !dpi && printable_size.IsEmpty();
+  }
 };
 
 struct ViewMsg_PrintPage_Params {
   // Parameters to render the page as a printed page. It must always be the same
   // value for all the document.
   ViewMsg_Print_Params params;
 
   // The page number is the indicator of the square that should be rendered
   // according to the layout specified in ViewMsg_Print_Params.
   int page_number;
@@ skipping 1510 matching lines @@
   }
 };
 
 }  // namespace IPC
 
 
 #define MESSAGES_INTERNAL_FILE "chrome/common/render_messages_internal.h"
 #include "chrome/common/ipc_message_macros.h"
 
 #endif  // CHROME_COMMON_RENDER_MESSAGES_H_