Document all 'canRepair: false' in repairES5.

Per <https://code.google.com/p/google-caja/issues/detail?id=1836>:
In SES, some problems are marked canRepair: false, not because no
possible repair exists, but because we no longer expect to see that
problem and so the repair code is not worth keeping around (r5524).

Add a comment explaining in each case why no repair is present, as a
best guess based on the history of each problem record.

@r5580

[MarkM, 2013-08-27 20:53:52]

LGTM

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
File src/com/google/caja/ses/repairES5.js (right):

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:3503: canRepair: false,  // Not repairable
Since one of your categories below is "// Not repairable without rewriting",
perhaps this and similar "Not repairable"s should be marked with that instead?

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:3936: canRepair: false,  // Not attempting
a repair
I don't understand what information "Not attempting a repair" adds. Why are we
not attempting a repair?

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:4014: canRepair: false,  // Not repairable
without rewriting
Actually not. All that would be required is a verifying parse. If we see any
syntax beyond what we want to recognize, including E4X, we'd reject.

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:4027: // 'repair' sets a flag to take
advantage of it.
All true. But additionally, even if we did want to repair this, it isn't
repairable without a rewrite.

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:4292: canRepair: false,  // Not repairable
... without a verifying parse.

[kpreid2, 2013-08-27 22:29:42]

Per <https://code.google.com/p/google-caja/issues/detail?id=1836>:
In SES, some problems are marked canRepair: false, not because no
possible repair exists, but because we no longer expect to see that
problem and so the repair code is not worth keeping around (r5524).

Add a comment explaining in each case why no repair is present, as a
best guess based on the history of each problem record.

[kpreid2, 2013-08-27 22:29:46]

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
File src/com/google/caja/ses/repairES5.js (right):

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:3503: canRepair: false,  // Not repairable
On 2013/08/27 20:53:52, MarkM wrote:
> Since one of your categories below is "// Not repairable without rewriting",
> perhaps this and similar "Not repairable"s should be marked with that instead?

Done.

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:3936: canRepair: false,  // Not attempting
a repair
On 2013/08/27 20:53:52, MarkM wrote:
> I don't understand what information "Not attempting a repair" adds. Why are we
> not attempting a repair?

I don't know! Do you?

What I didn't want to do was break the pattern of _every_ canRepair: false
having a comment of some sort (so that the next person to cut-and-paste a new
problem record is likely to include one in theirs).

Do you have a suggestion for a more informative comment (that is not a TODO)?

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:4014: canRepair: false,  // Not repairable
without rewriting
On 2013/08/27 20:53:52, MarkM wrote:
> Actually not. All that would be required is a verifying parse. If we see any
> syntax beyond what we want to recognize, including E4X, we'd reject.

Done.

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:4292: canRepair: false,  // Not repairable
On 2013/08/27 20:53:52, MarkM wrote:
> ... without a verifying parse.

Done.

[MarkM, 2013-08-27 23:09:24]

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
File src/com/google/caja/ses/repairES5.js (right):

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:3936: canRepair: false,  // Not attempting
a repair
On 2013/08/27 22:29:46, kpreid2 wrote:
> On 2013/08/27 20:53:52, MarkM wrote:
> > I don't understand what information "Not attempting a repair" adds. Why are
we
> > not attempting a repair?
> 
> I don't know! Do you?

I do, but I don't have an informative and non-pejorative short phrase. If a
platform suffers from this bug, it shows they take frozenness so unseriously
that it is not worth attempting a repair since we'll probably be unsafe in other
ways we don't know about anyway. Perhaps a more polite and still accurate point
is that we've never encountered an actual platform that both suffered from this
bug and was overall fixable.

> 
> What I didn't want to do was break the pattern of _every_ canRepair: false
> having a comment of some sort (so that the next person to cut-and-paste a new
> problem record is likely to include one in theirs).
> 
> Do you have a suggestion for a more informative comment (that is not a TODO)?

How about

// No known repairable platforms with this bug, so not worth repairing

[kpreid2, 2013-08-27 23:38:42]

Per <https://code.google.com/p/google-caja/issues/detail?id=1836>:
In SES, some problems are marked canRepair: false, not because no
possible repair exists, but because we no longer expect to see that
problem and so the repair code is not worth keeping around (r5524).

Add a comment explaining in each case why no repair is present, as a
best guess based on the history of each problem record.

[kpreid2, 2013-08-27 23:40:23]

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
File src/com/google/caja/ses/repairES5.js (right):

https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
src/com/google/caja/ses/repairES5.js:3936: canRepair: false,  // Not attempting
a repair
On 2013/08/27 23:09:24, MarkM wrote:
> // No known repairable platforms with this bug, so not worth repairing

Done, in slightly more words. Please confirm I didn't use that phrase in a case
where it doesn't apply.

[MarkM, 2013-08-27 23:43:23]

On 2013/08/27 23:40:23, kpreid2 wrote:
>
https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
> File src/com/google/caja/ses/repairES5.js (right):
> 
>
https://codereview.appspot.com/13242047/diff/1/src/com/google/caja/ses/repair...
> src/com/google/caja/ses/repairES5.js:3936: canRepair: false,  // Not
attempting
> a repair
> On 2013/08/27 23:09:24, MarkM wrote:
> > // No known repairable platforms with this bug, so not worth repairing
> 
> Done, in slightly more words. Please confirm I didn't use that phrase in a
case
> where it doesn't apply.

Confirmed.