Update gn

The currrent gn is quite old. The new gn, among other fixes, now supports
checking includes.

The values come from
https://chromium.googlesource.com/chromium/buildtools.git/+/893eb86b02b2571894e328f05551112b96df1cce

Change-Id: Ia2e47e18c7bbd3219a258fd6cc9063bf38588d00
Reviewed-on: https://skia-review.googlesource.com/129720
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/bin/fetch-gn b/bin/fetch-gn
index be2cb1a..d5e94a2 100755
--- a/bin/fetch-gn
+++ b/bin/fetch-gn
@@ -16,9 +16,9 @@
 
 dst = 'bin/gn.exe' if 'win32' in sys.platform else 'bin/gn'
 
-sha1 = '113f5b30a7cfae72015600a119590d45d64c0d0d' if 'linux'  in sys.platform else \
-       'b33a6d33c2b2f42762f902672ffdf4837fa1c662' if 'darwin' in sys.platform else \
-       'b1981c189f40c3ae42b965277ad1bc3449d26d2a'  # Windows
+sha1 = '2f27ff0b6118e5886df976da5effa6003d19d1ce' if 'linux'  in sys.platform else \
+       '9be792dd9010ce303a9c3a497a67bcc5ac8c7666' if 'darwin' in sys.platform else \
+       'eb69be2d984b4df60a8c21f598135991f0ad1742'  # Windows
 
 def sha1_of_file(path):
   h = hashlib.sha1()