In Date.parse() and new Date(), representations of the year 0 as -000000
must not be accepted. In the case of Date.parse(), they should yield NaN,
and in the case of new Date(), they should yield an invalid Date object,
whose valueOf() is NaN.
The values defined by the referenced files are not used by these tests.
This makes their inclusion superfluous, which needlessly increases the
time to execute the tests and may confuse some readers.
This function is equivalent to `$ERROR` (which is automatically included
in test environments). Remove the harness file that defines the
function, remove references to the file from test `includes` lists, and
update scripts to instead invoke the `$ERROR` function.
- Remove no longer needed noStrict flags.
- Change tests to use propertyHelper.js for strict mode compatibility.
- Add tests for return value of `delete` operator, e.g. `delete Array.prototype === false`.
- Add non-writable tests for global NaN property.
- Split some tests to run in strict mode.
- Change tests with global `var length` declaration to use a different variable name for browser environments.
- Merge duplicated tests symbol-data-property-configurable-non-strict and symbol-data-property-configurable-strict.
- Merge duplicated tests symbol-data-property-writable-non-strict and symbol-data-property-writable-strict.
- (And a small change in propertyHelper to reduce code duplication in function call.)
