Previously TryToName bailed out for Oddball keys (i.e. when passing true
or false as the key), which meant that for example the generic
KeyedLoadIC would always bail out to the %KeyedGetProperty runtime
function. But handling Oddball keys is fairly easy, since every oddball
value carries it's unique string representation. Adding just this case
to the CodeStubAssembler::TryToName method boosts this simple
micro-benchmark by a factor of 4x:

  const n = 1e7;
  const obj = {};
  const key = true;

  console.time('foo');
  for (let i = 0; i < n; ++i) {
    if (obj[key] === undefined) {
      obj[key] = key;
    }
  }
  console.timeEnd('foo');

It also shows on the ARES-6 ML benchmark and on several Speedometer
tests, where objects are being used as dictionaries and the developers
rely on the implicit ToString conversions on the property accesses.
In the ARES-6 ML benchmark, the number of calls to %KeyedGetProperty
is reduced by 137,758.

Bug: v8:6278, v8:6344, v8:6670
Change-Id: Iaa965e30be4c247682a67ec09543655df9b761d2
Reviewed-on: https://chromium-review.googlesource.com/599527Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47105}