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diff --git a/testing/mozbase/manifestparser/manifestparser/expression.py b/testing/mozbase/manifestparser/manifestparser/expression.py
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+++ b/testing/mozbase/manifestparser/manifestparser/expression.py
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+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import re
+import sys
+import traceback
+
+import six
+
+__all__ = ["parse", "ParseError", "ExpressionParser"]
+
+# expr.py
+# from:
+# http://k0s.org/mozilla/hg/expressionparser
+# http://hg.mozilla.org/users/tmielczarek_mozilla.com/expressionparser
+
+# Implements a top-down parser/evaluator for simple boolean expressions.
+# ideas taken from http://effbot.org/zone/simple-top-down-parsing.htm
+#
+# Rough grammar:
+# expr := literal
+#       | '(' expr ')'
+#       | expr '&&' expr
+#       | expr '||' expr
+#       | expr '==' expr
+#       | expr '!=' expr
+#       | expr '<' expr
+#       | expr '>' expr
+#       | expr '<=' expr
+#       | expr '>=' expr
+# literal := BOOL
+#          | INT
+#          | STRING
+#          | IDENT
+# BOOL   := true|false
+# INT    := [0-9]+
+# STRING := "[^"]*"
+# IDENT  := [A-Za-z_]\w*
+
+# Identifiers take their values from a mapping dictionary passed as the second
+# argument.
+
+# Glossary (see above URL for details):
+# - nud: null denotation
+# - led: left detonation
+# - lbp: left binding power
+# - rbp: right binding power
+
+
+class ident_token(object):
+    def __init__(self, scanner, value):
+        self.value = value
+
+    def nud(self, parser):
+        # identifiers take their value from the value mappings passed
+        # to the parser
+        return parser.value(self.value)
+
+
+class literal_token(object):
+    def __init__(self, scanner, value):
+        self.value = value
+
+    def nud(self, parser):
+        return self.value
+
+
+class eq_op_token(object):
+    "=="
+
+    def led(self, parser, left):
+        return left == parser.expression(self.lbp)
+
+
+class neq_op_token(object):
+    "!="
+
+    def led(self, parser, left):
+        return left != parser.expression(self.lbp)
+
+
+class lt_op_token(object):
+    "<"
+
+    def led(self, parser, left):
+        return left < parser.expression(self.lbp)
+
+
+class gt_op_token(object):
+    ">"
+
+    def led(self, parser, left):
+        return left > parser.expression(self.lbp)
+
+
+class le_op_token(object):
+    "<="
+
+    def led(self, parser, left):
+        return left <= parser.expression(self.lbp)
+
+
+class ge_op_token(object):
+    ">="
+
+    def led(self, parser, left):
+        return left >= parser.expression(self.lbp)
+
+
+class not_op_token(object):
+    "!"
+
+    def nud(self, parser):
+        return not parser.expression(100)
+
+
+class and_op_token(object):
+    "&&"
+
+    def led(self, parser, left):
+        right = parser.expression(self.lbp)
+        return left and right
+
+
+class or_op_token(object):
+    "||"
+
+    def led(self, parser, left):
+        right = parser.expression(self.lbp)
+        return left or right
+
+
+class lparen_token(object):
+    "("
+
+    def nud(self, parser):
+        expr = parser.expression()
+        parser.advance(rparen_token)
+        return expr
+
+
+class rparen_token(object):
+    ")"
+
+
+class end_token(object):
+    """always ends parsing"""
+
+
+# derived literal tokens
+
+
+class bool_token(literal_token):
+    def __init__(self, scanner, value):
+        value = {"true": True, "false": False}[value]
+        literal_token.__init__(self, scanner, value)
+
+
+class int_token(literal_token):
+    def __init__(self, scanner, value):
+        literal_token.__init__(self, scanner, int(value))
+
+
+class string_token(literal_token):
+    def __init__(self, scanner, value):
+        literal_token.__init__(self, scanner, value[1:-1])
+
+
+precedence = [
+    (end_token, rparen_token),
+    (or_op_token,),
+    (and_op_token,),
+    (lt_op_token, gt_op_token, le_op_token, ge_op_token, eq_op_token, neq_op_token),
+    (lparen_token,),
+]
+for index, rank in enumerate(precedence):
+    for token in rank:
+        token.lbp = index  # lbp = lowest left binding power
+
+
+class ParseError(Exception):
+    """error parsing conditional expression"""
+
+
+class ExpressionParser(object):
+    """
+    A parser for a simple expression language.
+
+    The expression language can be described as follows::
+
+        EXPRESSION ::= LITERAL | '(' EXPRESSION ')' | '!' EXPRESSION | EXPRESSION OP EXPRESSION
+        OP ::= '==' | '!=' | '<' | '>' | '<=' | '>=' | '&&' | '||'
+        LITERAL ::= BOOL | INT | IDENT | STRING
+        BOOL ::= 'true' | 'false'
+        INT ::= [0-9]+
+        IDENT ::= [a-zA-Z_]\w*
+        STRING ::= '"' [^\"] '"' | ''' [^\'] '''
+
+    At its core, expressions consist of booleans, integers, identifiers and.
+    strings. Booleans are one of *true* or *false*. Integers are a series
+    of digits. Identifiers are a series of English letters and underscores.
+    Strings are a pair of matching quote characters (single or double) with
+    zero or more characters inside.
+
+    Expressions can be combined with operators: the equals (==) and not
+    equals (!=) operators compare two expressions and produce a boolean. The
+    and (&&) and or (||) operators take two expressions and produce the logical
+    AND or OR value of them, respectively. An expression can also be prefixed
+    with the not (!) operator, which produces its logical negation.
+
+    Finally, any expression may be contained within parentheses for grouping.
+
+    Identifiers take their values from the mapping provided.
+    """
+
+    scanner = None
+
+    def __init__(self, text, valuemapping, strict=False):
+        """
+        Initialize the parser
+        :param text: The expression to parse as a string.
+        :param valuemapping: A dict mapping identifier names to values.
+        :param strict: If true, referencing an identifier that was not
+                       provided in :valuemapping: will raise an error.
+        """
+        self.text = text
+        self.valuemapping = valuemapping
+        self.strict = strict
+
+    def _tokenize(self):
+        """
+        Lex the input text into tokens and yield them in sequence.
+        """
+        if not ExpressionParser.scanner:
+            ExpressionParser.scanner = re.Scanner(
+                [
+                    # Note: keep these in sync with the class docstring above.
+                    (r"true|false", bool_token),
+                    (r"[a-zA-Z_]\w*", ident_token),
+                    (r"[0-9]+", int_token),
+                    (r'("[^"]*")|(\'[^\']*\')', string_token),
+                    (r"==", eq_op_token()),
+                    (r"!=", neq_op_token()),
+                    (r"<=", le_op_token()),
+                    (r">=", ge_op_token()),
+                    (r"<", lt_op_token()),
+                    (r">", gt_op_token()),
+                    (r"\|\|", or_op_token()),
+                    (r"!", not_op_token()),
+                    (r"&&", and_op_token()),
+                    (r"\(", lparen_token()),
+                    (r"\)", rparen_token()),
+                    (r"\s+", None),  # skip whitespace
+                ]
+            )
+        tokens, remainder = ExpressionParser.scanner.scan(self.text)
+        for t in tokens:
+            yield t
+        yield end_token()
+
+    def value(self, ident):
+        """
+        Look up the value of |ident| in the value mapping passed in the
+        constructor.
+        """
+        if self.strict:
+            return self.valuemapping[ident]
+        else:
+            return self.valuemapping.get(ident, "")
+
+    def advance(self, expected):
+        """
+        Assert that the next token is an instance of |expected|, and advance
+        to the next token.
+        """
+        if not isinstance(self.token, expected):
+            raise Exception("Unexpected token!")
+        self.token = six.next(self.iter)
+
+    def expression(self, rbp=0):
+        """
+        Parse and return the value of an expression until a token with
+        right binding power greater than rbp is encountered.
+        """
+        t = self.token
+        self.token = six.next(self.iter)
+        left = t.nud(self)
+        while rbp < self.token.lbp:
+            t = self.token
+            self.token = six.next(self.iter)
+            left = t.led(self, left)
+        return left
+
+    def parse(self):
+        """
+        Parse and return the value of the expression in the text
+        passed to the constructor. Raises a ParseError if the expression
+        could not be parsed.
+        """
+        try:
+            self.iter = self._tokenize()
+            self.token = six.next(self.iter)
+            return self.expression()
+        except Exception:
+            extype, ex, tb = sys.exc_info()
+            formatted = "".join(traceback.format_exception_only(extype, ex))
+            six.reraise(
+                ParseError,
+                ParseError(
+                    "could not parse: %s\nexception: %svariables: %s"
+                    % (self.text, formatted, self.valuemapping)
+                ),
+                tb,
+            )
+
+    __call__ = parse
+
+
+def parse(text, **values):
+    """
+    Parse and evaluate a boolean expression.
+    :param text: The expression to parse, as a string.
+    :param values: A dict containing a name to value mapping for identifiers
+                   referenced in *text*.
+    :rtype: the final value of the expression.
+    :raises: :py:exc::ParseError: will be raised if parsing fails.
+    """
+    return ExpressionParser(text, values).parse()