SRI: Add the 'integrity' attribute, and a SubresourceIntegrity runtime flag.

SRI: Add the 'integrity' attribute, and a SubresourceIntegrity runtime flag.

This patch adds a new flag to begin experimentation with the Subresource
Integrity specification[1], and begins adding the minimal amount of
functionality so we can test that the flag is working. That turns out to
be the 'integrity' attribute on various HTML elements that we'll use
later in order to do the actual verification.

Intent to Implement at [2].

[1]: http://w3c.github.io/webappsec/specs/subresourceintegrity/
[2]: https://groups.google.com/a/chromium.org/d/msg/blink-dev/hTDUpMk_TV8/t_rjlkKfgGgJ

BUG=355467
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170313

[Mike West, 2014-03-24 09:30:24]

Hello, friendly API OWNER. :)

Assuming no one objects to the intent to implement, would you mind taking a look
at this patch?

-mike

[jochen (gone - plz use gerrit), 2014-03-24 12:04:19]

https://codereview.chromium.org/208423011/diff/20001/Source/platform/RuntimeE...
File Source/platform/RuntimeEnabledFeatures.in (right):

https://codereview.chromium.org/208423011/diff/20001/Source/platform/RuntimeE...
Source/platform/RuntimeEnabledFeatures.in:110: SubresourceIntegrity
status=experimental
maybe start with test?

[Mike West, 2014-03-24 13:06:27]

On 2014/03/24 12:04:19, jochen wrote:
>
https://codereview.chromium.org/208423011/diff/20001/Source/platform/RuntimeE...
> File Source/platform/RuntimeEnabledFeatures.in (right):
> 
>
https://codereview.chromium.org/208423011/diff/20001/Source/platform/RuntimeE...
> Source/platform/RuntimeEnabledFeatures.in:110: SubresourceIntegrity
> status=experimental
> maybe start with test?

Sure. There's no way to turn that on with a command-line flag without piping
something through content, but I guess I can just enable it locally when I'm
screwing around with the implementation before exposing it to
experiment-friendly developers. :)

[jochen (gone - plz use gerrit), 2014-03-24 13:08:29]

ok, please wait for the blink-dev thread to resolve, otherwise lgtm

[Mike West, 2014-03-28 10:54:36]

On 2014/03/24 13:08:29, jochen wrote:
> ok, please wait for the blink-dev thread to resolve, otherwise lgtm

There were indeed objections to the intent; I think they've been resolved in a
way which would allow a minimal implementation to land in order to evaluate the
impact:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/hTDUpMk_TV8/inGc_jhD...

Let's see how it goes.

[Mike West, 2014-03-28 10:54:46]

The CQ bit was checked by mkwst@chromium.org

[commit-bot: I haz the power, 2014-03-28 10:54:49]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mkwst@chromium.org/208423011/40001

[commit-bot: I haz the power, 2014-03-28 11:40:26]

Change committed as 170313