Move GetPrintHandler to CefClient (see issue #2196)

This new location is preferred because we now know the associated CefBrowser
for all CefPrintHandler callbacks.

tests/cefclient/browser/client_handler.cc

@@ -259,6 +259,7 @@ ClientHandler::ClientHandler(Delegate* delegate,
 #if defined(OS_LINUX)
   // Provide the GTK-based dialog implementation on Linux.
   dialog_handler_ = new ClientDialogHandlerGtk();
+  print_handler_ = new ClientPrintHandlerGtk();
 #endif
 
   resource_manager_ = new CefResourceManager();