Implement "replacement" text encoding.

Implement "replacement" text encoding.

The WHATWG Encoding Standard redefines certain legacy encodings
as that are only used as XSS attack vectors as aliases for an
abstract "replacement" encoding.

* Decode (of resources) terminates with a single U+FFFD.
* Encode (e.g. for form submissions) is treated as UTF-8.

This is dependent on http://crrev.com/269593009

BUG=277037
R=jshin@chromium.org,eseidel@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173954

[jsbell, 2014-05-02 18:39:39]

This is part 2 of 3. The full sequence is:

1. API/test cleanup - https://codereview.chromium.org/269593009
2. New codec - https://codereview.chromium.org/265973003
3. Block use by name - https://codereview.chromium.org/261013007

[jungshik at Google, 2014-05-05 21:51:04]

On 2014/05/02 18:39:39, jsbell wrote:
> This is part 2 of 3. The full sequence is:
> 
> 1. API/test cleanup - https://codereview.chromium.org/269593009
> 2. New codec - https://codereview.chromium.org/265973003
> 3. Block use by name - https://codereview.chromium.org/261013007

Did you make a new CL for replacement encoding implementation)?

[jsbell, 2014-05-05 21:58:51]

On 2014/05/05 21:51:04, Jungshik Shin wrote:
> On 2014/05/02 18:39:39, jsbell wrote:
> > This is part 2 of 3. The full sequence is:
> > 
> > 1. API/test cleanup - https://codereview.chromium.org/269593009
> > 2. New codec - https://codereview.chromium.org/265973003
> > 3. Block use by name - https://codereview.chromium.org/261013007
> 
> Did you make a new CL for replacement encoding implementation)?

Yes. That's what the 1/2/3 are above.

[jsbell, 2014-05-08 21:14:42]

On 2014/05/05 21:58:51, jsbell wrote:
> On 2014/05/05 21:51:04, Jungshik Shin wrote:
> > On 2014/05/02 18:39:39, jsbell wrote:
> > > This is part 2 of 3. The full sequence is:
> > > 
> > > 1. API/test cleanup - https://codereview.chromium.org/269593009
> > > 2. New codec - https://codereview.chromium.org/265973003
> > > 3. Block use by name - https://codereview.chromium.org/261013007
> > 
> > Did you make a new CL for replacement encoding implementation)?
> 
> Yes. That's what the 1/2/3 are above.

Just to be clear, I split things up into three patches. #1 is just cleanup/tests
for the API, #2 (this patch) is the new replacement encoding implementation (and
tests), and #3 prevents it from being used by name (and tests).

They need to land one by one, so I'm waiting on a review on #1.

[eseidel, 2014-05-09 06:39:44]

Why does this want to subclass the UTF8 encoding?

[eseidel, 2014-05-09 06:40:08]

Ah, because any time you encode anything with one of these you get utf8? it's
only decode which is special?

[jsbell, 2014-05-09 15:31:09]

On 2014/05/09 06:40:08, eseidel wrote:
> Ah, because any time you encode anything with one of these you get utf8? it's
> only decode which is special?

Yep. And specifically UTF-8, not your browsers default locale. 

I could keep UTF8 final, and make it has-a instead of is-a but there are enough
methods that would require proxying I thought this was cleaner, unless perf
tells otherwise. (And the methods are already virtual so I'm not expecting a
perf hit.)

[eseidel, 2014-05-09 17:33:29]

Nah, dispatch to decoders can't be perf sensitive.  They do so much
malloc/copying which would dominate anyway.

lgtm.

[jsbell, 2014-05-13 08:16:26]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2014-05-13 08:16:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jsbell@chromium.org/265973003/1

[commit-bot: I haz the power, 2014-05-13 09:34:46]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/7067)

[jsbell, 2014-05-13 09:36:06]

The CQ bit was unchecked by jsbell@chromium.org

[jsbell, 2014-05-13 10:43:39]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2014-05-13 10:43:55]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jsbell@chromium.org/265973003/20001

[jsbell, 2014-05-13 11:54:35]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2014-05-13 11:54:42]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jsbell@chromium.org/265973003/40001

[commit-bot: I haz the power, 2014-05-13 13:08:27]

Change committed as 173954