Add gdb.printing import in gdb chrome python file for issue 226278 (gdb

tools/gdb/gdb_chrome.py

 # 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.
 
 """GDB support for Chrome types.
 
 Add this to your gdb by amending your ~/.gdbinit as follows:
   python
   import sys
   sys.path.insert(0, "/path/to/tools/gdb/")
   import gdb_chrome
   end
 
 This module relies on the WebKit gdb module already existing in
 your Python path.
 
 Use
   (gdb) p /r any_variable
 to print |any_variable| without using any printers.
 """
 
 import datetime
 import gdb
+import gdb.printing
 import webkit
 
 # When debugging this module, set the below variable to True, and then use
 #   (gdb) python del sys.modules['gdb_chrome']
 #   (gdb) python import gdb_chrome
 # to reload.
 _DEBUGGING = False
 
 
 pp_set = gdb.printing.RegexpCollectionPrettyPrinter("chromium")
@@ skipping 253 matching lines @@
         yield ('sudden_termination_allowed_',
                self.val['sudden_termination_allowed_'])
         yield ('ignore_input_events_', self.val['ignore_input_events_'])
         yield ('is_guest_', self.val['is_guest_'])
 pp_set.add_printer('content::RenderProcessHostImpl',
                    '^content::RenderProcessHostImpl$',
                    RenderProcessHostImplPrinter)
 
 
 gdb.printing.register_pretty_printer(gdb, pp_set, replace=_DEBUGGING)