Index: common.gypi
===================================================================
--- common.gypi	(revision 70742)
+++ common.gypi	(working copy)
@@ -9,6 +9,9 @@
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
   'variables': {
+    # Directory for CEF source files. This will be set by cef.gypi.
+    'cef_directory%' : '',
+
     # Putting a variables dict inside another variables dict looks kind of
     # weird.  This is done so that 'host_arch', 'chromeos', etc are defined as
     # variables within the outer variables dict here.  This is necessary
Index: win/system.gyp
===================================================================
--- win/system.gyp	(revision 70742)
+++ win/system.gyp	(working copy)
@@ -22,6 +22,13 @@
           'action': ['', '<@(_inputs)'],
         },
       ],
+      'conditions': [
+        ['cef_directory!=""', {
+          'dependencies': [
+            '../../<(cef_directory)/cef.gyp:patcher',
+          ],
+        }],
+      ],
     },
   ],
 }