Functions like DataView.prototype.getUint8 should have length 1,
and DataView.prototype.setUint8 should have length 2, as their
endianness arguments are optional. Additionally,
TypedArray.prototype.set.length should be 2. This follows the ES2015
specification, and a new test262 test tests for it. This patch
fixes the functions' lengths.

R=adamk

Review URL: https://codereview.chromium.org/1636953003

Cr-Commit-Position: refs/heads/master@{#33531}