ES6 computed property names

This adds support for computed property names, under the flag
--harmony-computed-property-names, for both object literals and
classes.

BUG=v8:3754
LOG=Y

Review URL: https://codereview.chromium.org/795573005

Cr-Commit-Position: refs/heads/master@{#25821}
Internalize strings being stored into uninitialized property cells

Review URL: https://codereview.chromium.org/804993002

Cr-Commit-Position: refs/heads/master@{#25822}
Add fast path for array indices to Runtime_HasOwnProperty

Review URL: https://codereview.chromium.org/803833004

Cr-Commit-Position: refs/heads/master@{#25823}
MIPS: [turbofan] Remove the no-context hack for JSToNumber.

Port d211608a3eb7ef3da4d04fd4f5a8540dedbd1faa

Original commit message:
The ToNumberStub is now able to handle all plain primitives (Numbers,
Booleans, Null, Undefined and Strings) without context access.

TEST=cctest,mjsunit,unittests
BUG=

Review URL: https://codereview.chromium.org/803973002

Cr-Commit-Position: refs/heads/master@{#25824}
Revert of ES6 computed property names (patchset #9 id:160001 of https://codereview.chromium.org/795573005/)

Reason for revert:
Crashes on Win32

http://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%201/builds/1357

Test: mjsunit/harmony/computed-property-names
Flags: --stress-opt --always-opt
Command: build\Release\d8.exe --test --random-seed=-233815021 --stress-opt --always-opt --nohard-abort --nodead-code-elimination --nofold-constants --harmony-computed-property-names test\mjsunit\mjsunit.js test\mjsunit\harmony\computed-property-names.js

Run #1
Exit code: -1073741819
Result: CRASH
Expected outcomes: PASS

Run #2
Exit code: -1073741819
Result: CRASH
Expected outcomes: PASS

Run #3
Exit code: -1073741819
Result: CRASH
Expected outcomes: PASS

Original issue's description:
> ES6 computed property names
>
> This adds support for computed property names, under the flag
> --harmony-computed-property-names, for both object literals and
> classes.
>
> BUG=v8:3754
> LOG=Y

TBR=dslomov@chromium.org,wingo@igalia.com
NOTREECHECKS=true
NOTRY=true
BUG=v8:3754

Review URL: https://codereview.chromium.org/809433002

Cr-Commit-Position: refs/heads/master@{#25825}
Ship ES6 classes.

R=arv@chromium.org
BUG=v8:3330
LOG=Y

Review URL: https://codereview.chromium.org/808433002

Cr-Commit-Position: refs/heads/master@{#25826}