Speed up typed array constructors.  - Avoid calls into ToPositiveInteger for valid cases of 'undefined' arguments.   (Otherwise it calls into runtime).  - Reduce the checks performed in case offset for TypedArrayFromArrayBuffer   constructor is called with no offset argument.
Speed up typed array constructors.
 - Avoid calls into ToPositiveInteger for valid cases of 'undefined' arguments.
  (Otherwise it calls into runtime).
 - Reduce the checks performed in case offset for TypedArrayFromArrayBuffer
  constructor is called with no offset argument.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/59763010

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@17567 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh