[es6] implement destructuring assignment [clean diff]

[es6] implement destructuring assignment

Implement destructuring assignment on top of the parsing implementation (https://crrev.com/1309813007) and the |do expressions| implementation (https://crrev.com/1399893002).

BUG=v8:811
LOG=N
R=adamk, wingo, aperez, conradw, dehrenberg

[caitp (gmail), 2015-10-19 11:17:39]

https://codereview.chromium.org/1411203002/diff/1/src/parser.cc
File src/parser.cc (right):

https://codereview.chromium.org/1411203002/diff/1/src/parser.cc#newcode3613
src/parser.cc:3613: if (value->IsAssignment()) {
I'll make all of this completion-value-saving code much simpler, shortly

[caitp (gmail), 2015-10-19 11:17:54]

Description was changed from

==========
[es6] implement destructuring assignment

BUG=v8:811
LOG=N
R=adamk, wingo, aperez, conradw, dehrenberg
==========

to

==========
[es6] implement destructuring assignment

BUG=v8:811
LOG=N
R=adamk, wingo, aperez, conradw, dehrenberg
==========

[caitp (gmail), 2015-10-19 12:09:13]

Description was changed from

==========
[es6] implement destructuring assignment

BUG=v8:811
LOG=N
R=adamk, wingo, aperez, conradw, dehrenberg
==========

to

==========
[es6] implement destructuring assignment

Implement destructuring assignment on top of the parsing implementation
(https://crrev.com/1309813007) and the |do expressions| implementation
(https://crrev.com/1399893002).

BUG=v8:811
LOG=N
R=adamk, wingo, aperez, conradw, dehrenberg
==========

[caitp (gmail), 2015-10-19 12:10:50]

https://codereview.chromium.org/1411203002/diff/20001/src/pattern-rewriter.cc
File src/pattern-rewriter.cc (right):

https://codereview.chromium.org/1411203002/diff/20001/src/pattern-rewriter.cc...
src/pattern-rewriter.cc:252: block_->statements()->Add(
I was hoping this would help reduce the number of stack slots used, but it
doesn't seem to make a difference. So maybe worth removing all of that