The Tor Browser / file revision

 // Turn on strict mode and warnings-as-errors mode.

 if (options().split().indexOf('strict') == -1)

     options('strict');

 if (options().split().indexOf('werror') == -1)

     options('werror');

 function expectSyntaxError(stmt) {

     print(stmt);

     var result = 'no error';

     try {

         Function(stmt);

     } catch (exc) {

         result = exc.constructor.name;

     }

     assertEq(result, 'SyntaxError');

 }

 function test(expr) {

     // Without extra parentheses, expect an error.

     expectSyntaxError('if (' + expr + ') {};');

     // Extra parentheses silence the warning/error.

     Function('if ((' + expr + ')) {};');

 }

 // Overparenthesized assignment in a condition should not be a strict error.

 test('a = 0');

 test('a = (f(), g)');

 test('a = b || c > d');

 expectSyntaxError('if (a == 0);');

 reportCompare('passed', 'passed', 'Overparenthesized assignment in a condition should not be a strict error.');