diff --git a/framework/validate.py b/framework/validate.py
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+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+"""A set of Python input field validators."""
+from __future__ import print_function
+from __future__ import division
+from __future__ import absolute_import
+
+import re
+
+# RFC 2821-compliant email address regex
+#
+# Please see sections "4.1.2 Command Argument Syntax" and
+# "4.1.3 Address Literals" of:  http://www.faqs.org/rfcs/rfc2821.html
+#
+# The following implementation is still a subset of RFC 2821.  Fully
+# double-quoted <user> parts are not supported (since the RFC discourages
+# their use anyway), and using the backslash to escape other characters
+# that are normally invalid, such as commas, is not supported.
+#
+# The groups in this regular expression are:
+#
+# <user>: all of the valid non-quoted portion of the email address before
+#   the @ sign (not including the @ sign)
+#
+# <domain>: all of the domain name between the @ sign (but not including it)
+#   and the dot before the TLD (but not including that final dot)
+#
+# <tld>: the top-level domain after the last dot (but not including that
+#   final dot)
+#
+_RFC_2821_EMAIL_REGEX = r"""(?x)
+  (?P<user>
+    # Part of the username that comes before any dots that may occur in it.
+    # At least one of the listed non-dot characters is required before the
+    # first dot.
+    [-a-zA-Z0-9!#$%&'*+/=?^_`{|}~]+
+
+    # Remaining part of the username that starts with the dot and
+    # which may have other dots, if such a part exists.  Only one dot
+    # is permitted between each "Atom", and a trailing dot is not permitted.
+    (?:[.][-a-zA-Z0-9!#$%&'*+/=?^_`{|}~]+)*
+  )
+
+  # Domain name, where subdomains are allowed.  Also, dashes are allowed
+  # given that they are preceded and followed by at least one character.
+  @(?P<domain>
+    (?:[0-9a-zA-Z]       # at least one non-dash
+       (?:[-]*           # plus zero or more dashes
+          [0-9a-zA-Z]+   # plus at least one non-dash
+       )*                # zero or more of dashes followed by non-dashes
+    )                    # one required domain part (may be a sub-domain)
+
+    (?:\.                # dot separator before additional sub-domain part
+       [0-9a-zA-Z]       # at least one non-dash
+       (?:[-]*           # plus zero or more dashes
+          [0-9a-zA-Z]+   # plus at least one non-dash
+       )*                # zero or more of dashes followed by non-dashes
+    )*                   # at least one sub-domain part and a dot
+   )
+  \.                     # dot separator before TLD
+
+  # TLD, the part after 'usernames@domain.' which can consist of 2-9
+  # letters.
+  (?P<tld>[a-zA-Z]{2,9})
+  """
+
+# object used with <re>.search() or <re>.sub() to find email addresses
+# within a string (or with <re>.match() to find email addresses at the
+# beginning of a string that may be followed by trailing characters,
+# since <re>.match() implicitly anchors at the beginning of the string)
+RE_EMAIL_SEARCH = re.compile(_RFC_2821_EMAIL_REGEX)
+
+# object used with <re>.match to find strings that contain *only* a single
+# email address (by adding the end-of-string anchor $)
+RE_EMAIL_ONLY = re.compile('^%s$' % _RFC_2821_EMAIL_REGEX)
+
+_SCHEME_PATTERN = r'(?:https?|ftp)://'
+_SHORT_HOST_PATTERN = (
+    r'(?=[a-zA-Z])[-a-zA-Z0-9]*[a-zA-Z0-9](:[0-9]+)?'
+    r'/'  # Slash is manditory for short host names.
+    r'[^\s]*'
+    )
+_DOTTED_HOST_PATTERN = (
+    r'[-a-zA-Z0-9.]+\.[a-zA-Z]{2,9}(:[0-9]+)?'
+    r'(/[^\s]*)?'
+    )
+_URL_REGEX = r'%s(%s|%s)' % (
+    _SCHEME_PATTERN, _SHORT_HOST_PATTERN, _DOTTED_HOST_PATTERN)
+
+# A more complete URL regular expression based on a combination of the
+# existing _URL_REGEX and the pattern found for URI regular expressions
+# found in the URL RFC document. It's detailed here:
+# http://www.ietf.org/rfc/rfc2396.txt
+RE_COMPLEX_URL = re.compile(r'^%s(\?([^# ]*))?(#(.*))?$' % _URL_REGEX)
+
+
+def IsValidEmail(s):
+  """Return true iff the string is a properly formatted email address."""
+  return RE_EMAIL_ONLY.match(s)
+
+
+def IsValidMailTo(s):
+  """Return true iff the string is a properly formatted mailto:."""
+  return s.startswith('mailto:') and RE_EMAIL_ONLY.match(s[7:])
+
+
+def IsValidURL(s):
+  """Return true iff the string is a properly formatted web or ftp URL."""
+  return RE_COMPLEX_URL.match(s)