Add cloud_print to the GN build.

cloud_print/virtual_driver/win/virtual_driver.gypi

Index: cloud_print/virtual_driver/win/virtual_driver.gypi
diff --git a/cloud_print/virtual_driver/win/virtual_driver.gypi b/cloud_print/virtual_driver/win/virtual_driver.gypi
index 41b2a97fe0feba292854492766c9030ccfebf893..159588343af605684a1c4176cef903af7c642dc2 100644
--- a/cloud_print/virtual_driver/win/virtual_driver.gypi
+++ b/cloud_print/virtual_driver/win/virtual_driver.gypi
@@ -16,6 +16,7 @@
   },
   'targets' : [
     {
+      # GN version: //cloud_print/virtual_driver/win
       'target_name': 'virtual_driver_lib<(virtual_driver_suffix)',
       'type': 'static_library',
       'sources': [
@@ -28,6 +29,7 @@
       ],
     },
     {
+      # GN version: //cloud_print/virtual_driver/win/port_monitor:lib
       'target_name': 'gcp_portmon_lib<(virtual_driver_suffix)',
       'type': 'static_library',
       'sources': [
@@ -39,6 +41,7 @@
       ],
     },
     {
+      # GN version: //cloud_print/virtual_driver/win/port_monitor
       'target_name': 'gcp_portmon<(virtual_driver_suffix)',
       'type': 'loadable_module',
       'sources': [