Fix gitlab known-good to correct commits.

Also add update_glslang_sources_khr.py
diff --git a/known_good_khr.json b/known_good_khr.json
index 2d6674d..e1a7a0f 100644
--- a/known_good_khr.json
+++ b/known_good_khr.json
@@ -5,14 +5,14 @@
       "site" : "gitlab",
       "subrepo" : "spirv/spirv-tools",
       "subdir" : "External/spirv-tools",
-      "commit" : "063dbea0f19a3926b81a34fa8dc5479fa7969739"
+      "commit" : "65457244d0135e91815fef57dc662f9b39232284"
     },
     {
       "name" : "spirv-tools/external/spirv-headers",
       "site" : "gitlab",
       "subrepo" : "spirv/SPIRV-Headers",
       "subdir" : "External/spirv-tools/external/spirv-headers",
-      "commit" : "77240d9e86c6ff135f6de8c7b89a0099a2d90e16"
+      "commit" : "854b5dda6149c481d6faf0b9c760c311ab45b05d"
     }
   ]
 }
diff --git a/update_glslang_sources_khr.py b/update_glslang_sources_khr.py
new file mode 100755
index 0000000..52031d4
--- /dev/null
+++ b/update_glslang_sources_khr.py
@@ -0,0 +1,152 @@
+#!/usr/bin/env python
+
+# Copyright 2017 The Glslang Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Get source files for Glslang and its dependencies from public repositories.
+"""
+
+from __future__ import print_function
+
+import argparse
+import json
+import distutils.dir_util
+import os.path
+import subprocess
+import sys
+
+KNOWN_GOOD_FILE = 'known_good_khr.json'
+
+# Maps a site name to its hostname.
+SITE_TO_HOST = { 'github' : 'github.com',
+                 'gitlab' : 'gitlab.khronos.org' }
+
+VERBOSE = True
+
+
+def command_output(cmd, directory, fail_ok=False):
+    """Runs a command in a directory and returns its standard output stream.
+
+    Captures the standard error stream.
+
+    Raises a RuntimeError if the command fails to launch or otherwise fails.
+    """
+    if VERBOSE:
+        print('In {d}: {cmd}'.format(d=directory, cmd=cmd))
+    p = subprocess.Popen(cmd,
+                         cwd=directory,
+                         stdout=subprocess.PIPE)
+    (stdout, _) = p.communicate()
+    if p.returncode != 0 and not fail_ok:
+        raise RuntimeError('Failed to run {} in {}'.format(cmd, directory))
+    if VERBOSE:
+        print(stdout)
+    return stdout
+
+
+def command_retval(cmd, directory):
+    """Runs a command in a directory and returns its return value.
+
+    Captures the standard error stream.
+    """
+    p = subprocess.Popen(cmd,
+                         cwd=directory,
+                         stdout=subprocess.PIPE)
+    (stdout, _) = p.communicate()
+    return p.returncode
+
+
+class GoodCommit(object):
+    """Represents a good commit for a repository."""
+
+    def __init__(self, json):
+        """Initializes this good commit object.
+
+        Args:
+        'json':  A fully populated JSON object describing the commit.
+        """
+        self._json = json
+        self.name = json['name']
+        self.site = json['site']
+        self.subrepo = json['subrepo']
+        self.subdir = json['subdir'] if ('subdir' in json) else '.'
+        self.commit = json['commit']
+
+    def GetUrl(self, style='https'):
+        """Returns the URL for the repository."""
+        host = SITE_TO_HOST[self.site]
+        sep = '/' if (style is 'https') else ':'
+        return '{style}://{host}{sep}{subrepo}'.format(
+                    style=style,
+                    host=host,
+                    sep=sep,
+                    subrepo=self.subrepo)
+
+    def AddRemote(self):
+        """Add the remote 'known-good' if it does not exist."""
+        print('Ignore "fatal" errors for missing known-good remote:')
+        if command_retval(['git', 'remote', 'show', 'known-good'], self.subdir) != 0:
+            command_output(['git', 'remote', 'add', 'known-good', self.GetUrl()], self.subdir)
+
+    def HasCommit(self):
+        """Check if the repository contains the known-good commit."""
+        return 0 == subprocess.call(['git', 'rev-parse', '--verify', '--quiet',
+                                     self.commit + "^{commit}"],
+                                    cwd=self.subdir)
+
+    def Clone(self):
+        distutils.dir_util.mkpath(self.subdir)
+        command_output(['git', 'clone', self.GetUrl(), '.'], self.subdir)
+
+    def Fetch(self):
+        command_output(['git', 'fetch', 'known-good'], self.subdir)
+
+    def Checkout(self):
+        if not os.path.exists(os.path.join(self.subdir,'.git')):
+            self.Clone()
+        self.AddRemote()
+        if not self.HasCommit():
+            self.Fetch()
+        command_output(['git', 'checkout', self.commit], self.subdir)
+
+
+def GetGoodCommits():
+    """Returns the latest list of GoodCommit objects."""
+    with open(KNOWN_GOOD_FILE) as known_good:
+        return [GoodCommit(c) for c in json.loads(known_good.read())['commits']]
+
+
+def main():
+    parser = argparse.ArgumentParser(description='Get Glslang source dependencies at a known-good commit')
+    parser.add_argument('--dir', dest='dir', default='.',
+                        help="Set target directory for Glslang source root. Default is \'.\'.")
+
+    args = parser.parse_args()
+
+    commits = GetGoodCommits()
+
+    distutils.dir_util.mkpath(args.dir)
+    print('Change directory to {d}'.format(d=args.dir))
+    os.chdir(args.dir)
+
+    # Create the subdirectories in sorted order so that parent git repositories
+    # are created first.
+    for c in sorted(commits, key=lambda x: x.subdir):
+        print('Get {n}\n'.format(n=c.name))
+        c.Checkout()
+    sys.exit(0)
+
+
+if __name__ == '__main__':
+    main()