Use service process to collect printers.

chrome/common/service_messages.h

 // 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.
 
 // Multiply-included message file, no traditional include guard.
 #include <string>
 #include <vector>
 
 #include "base/values.h"
 #include "chrome/common/cloud_print/cloud_print_proxy_info.h"
@@ skipping 19 matching lines @@
 // Tell the service process to disable the cloud proxy.
 IPC_MESSAGE_CONTROL0(ServiceMsg_DisableCloudPrintProxy)
 
 // Requests a message back on the current status of the cloud print proxy
 // (whether it is enabled, the email address and the proxy id).
 IPC_MESSAGE_CONTROL0(ServiceMsg_GetCloudPrintProxyInfo)
 
 // Requests a message back with serialized UMA histograms.
 IPC_MESSAGE_CONTROL0(ServiceMsg_GetHistograms)
 
+// Requests a message back with all available printers.
+IPC_MESSAGE_CONTROL0(ServiceMsg_GetPrinters)
+
 // Tell the service process to shutdown.
 IPC_MESSAGE_CONTROL0(ServiceMsg_Shutdown)
 
 // Tell the service process that an update is available.
 IPC_MESSAGE_CONTROL0(ServiceMsg_UpdateAvailable)
 
 //-----------------------------------------------------------------------------
 // Service process host messages:
 // These are messages from the service process to the browser.
 // Sent as a response to a request for cloud print proxy info
 IPC_MESSAGE_CONTROL1(ServiceHostMsg_CloudPrintProxy_Info,
                      cloud_print::CloudPrintProxyInfo /* proxy info */)
 
 // Sent as a response to ServiceMsg_GetHistograms.
 IPC_MESSAGE_CONTROL1(ServiceHostMsg_Histograms,
                      std::vector<std::string> /* pickled_histograms */)
+
+// Sent as a response to ServiceMsg_GetPrinters.
+IPC_MESSAGE_CONTROL1(ServiceHostMsg_Printers,
+                     std::vector<std::string> /* printers */)