ES6: String(symbol) should work like symbol.toString

ES6: String(symbol) should work like symbol.toString

Using String as a function and passing a symbol should return the
same  value as if Symbol.prototype.toString was called.

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-string-constructor-string-value

BUG=v8:3554
LOG=Y
R=rossberg@chromium.org, rossberg

Committed: https://code.google.com/p/v8/source/detail?r=23923

[rossberg, 2014-09-12 12:56:38]

https://codereview.chromium.org/564863002/diff/1/src/string.js
File src/string.js (right):

https://codereview.chromium.org/564863002/diff/1/src/string.js#newcode15
src/string.js:15: if (%_ArgumentsLength() == 0) return '';
We could avoid duplicating this case by pulling out

  if (%_ArgumentsLength() == 0) x = '';

https://codereview.chromium.org/564863002/diff/1/src/string.js#newcode17
src/string.js:17: return TO_STRING_INLINE(x);
Nit: merge the returns into a ?:

[arv (Not doing code reviews), 2014-09-12 15:24:27]

Code review feedback

[arv (Not doing code reviews), 2014-09-12 15:25:21]

PTAL

[rossberg, 2014-09-12 15:32:09]

lgtm

[arv (Not doing code reviews), 2014-09-12 16:17:32]

Committed patchset #2 (id:20001) manually as 23923 (presubmit successful).