Throw a more descriptive exception when blocking 'eval' via CSP.

Throw a more descriptive exception when blocking 'eval' via CSP.

BUG=140191
R=svenpanne@chromium.org,mkwst@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=12525

[ulan, 2012-08-21 12:02:53]

Please take a look.

[Use mkwst_at_chromium.org plz., 2012-08-21 12:45:23]

On 2012/08/21 12:02:53, ulan wrote:
> Please take a look.

Thank you, Ulan. This LGTM, but I have no idea what I'm doing. :)

It looks like this would allow WebKit to request the current error string? If
so, we should be able to solve the WebInspector issue you flagged on the webkit
bug by reading the error message, toggling the setting, and then writing the
error message back. Not pretty, but it would work.

[ulan, 2012-08-21 13:08:30]

In that case we would need to export the
ErrorMessageForCodeGenerationFromStrings() function as an API function. 

I wonder if it would be cleaner to just add the 'eval blocking' flag and the
error message as two independent fields to the context. Then we would export
SetErrorMessageForCodeGenerationFromStrings(String) function in the API and the
AllowCodeGenerationFromStrings(bool) would remain unchanged. This would allow
the web inspector to toggle the flag without changing the error message.

[Sven Panne, 2012-08-21 14:19:57]

LGTM with one nit: error_message_for_code_gen_from_strings's type in
Haskell-speak is basically 'Maybe String', this is not reflected in the field's
name, but I can't come up with a better one. So if somebody has a better idea,
please rename that field.

[Sven Panne, 2012-09-17 09:56:13]

lgtm