port 322ffda3 (r33265)

  original commit message:
  Also migrate the Number constructor to a native builtin, using the
  same mechanism already used by the String constructor. Otherwise just
  parsing and compiling the Number constructor to optimized code already
  eats 2ms on desktop for no good reason, and the resulting optimized
  code is not even close to awesome.

  Drive-by-fix: Use correct context for the [[Construct]] case of the
  String constructor as well, and share some code with it.

BUG=

Review URL: https://codereview.chromium.org/1581313002

Cr-Commit-Position: refs/heads/master@{#33280}