This reverts commit b690cb67be9b487eb10156c03e2c00869e88cc9d, reversing
changes made to 50dd431dffe5cf86e9064a652d6b01dbbe542cf0. This is
necessary because the reverted changeset reduced coverage by an unknown
extent.
Fixes gh-696
As pointed in gh-696, the ArrayBuffer ctor won't throw a RangeError when
invoked without arguments.
Instead of fixing the invalid assertion, this commit removes it as the
coverage for subclassing is already satisfied by the use of slice.