Fix broken include path for directwrite backend

R=borenet@google.com

Review URL: https://codereview.chromium.org/16325006

git-svn-id: http://skia.googlecode.com/svn/trunk/gyp@9400 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/ports.gyp b/ports.gyp
index 3422b8e..af6229e 100644
--- a/ports.gyp
+++ b/ports.gyp
@@ -13,6 +13,7 @@
         '../include/images',
         '../include/ports',
         '../include/utils',
+        '../include/utils/win',
         '../include/xml',
         '../src/core',
         '../src/lazy',