Make SVGTextContentElement methods behave consistently with Firefox and IE

Make SVGTextContentElement methods behave consistently with Firefox and IE

Make SVGTextContentElement methods behave consistently with Firefox 23 and
IE10:
- We should not throw when negative values are passed in arguments as long
  as they wrap to a valid positive index.
- Arguments should be mandatory

Also fixed a bug in SVGTextContentElement.getSubStringLength() where the
wrong result would be returned if the nchars argument was
too large due to an overflow. To avoid this issue, we clamp the nchars
value to (numberOfChars - charnum) similarly to what is done in
SVGTextContentElement.selectSubString(), and as per the specification:
http://www.w3.org/TR/SVG2/text.html#__svg__SVGTextContentElement__getSubStringLength

BUG=268269
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=156036

[do-not-use, 2013-08-12 08:59:12]

I validated the behavior of other browsers using:
http://jsfiddle.net/hC7Cb/15/

[arv (Not doing code reviews), 2013-08-12 13:42:21]

Typo in CL description

passed in arguments

or

passed as argument

[arv (Not doing code reviews), 2013-08-12 13:42:57]

One more CL description issue

"where the wrong result would return the wrong result"

now on to the real code review.

[arv (Not doing code reviews), 2013-08-12 13:47:21]

LGTM

https://codereview.chromium.org/22798002/diff/1/LayoutTests/svg/text/svgtextc...
File LayoutTests/svg/text/svgtextcontentelement-methods-parameters.html (right):

https://codereview.chromium.org/22798002/diff/1/LayoutTests/svg/text/svgtextc...
LayoutTests/svg/text/svgtextcontentelement-methods-parameters.html:25:
actual_point = _actual_point;
Do not use underscores in identifier names.

[do-not-use, 2013-08-12 13:52:54]

On 2013/08/12 13:47:21, arv wrote:
> LGTM
> 
>
https://codereview.chromium.org/22798002/diff/1/LayoutTests/svg/text/svgtextc...
> File LayoutTests/svg/text/svgtextcontentelement-methods-parameters.html
(right):
> 
>
https://codereview.chromium.org/22798002/diff/1/LayoutTests/svg/text/svgtextc...
> LayoutTests/svg/text/svgtextcontentelement-methods-parameters.html:25:
> actual_point = _actual_point;
> Do not use underscores in identifier names.

Done, thanks.

[do-not-use, 2013-08-12 20:57:18]

+jsbell

[do-not-use, 2013-08-13 10:50:12]

+jochen

[jochen (gone - plz use gerrit), 2013-08-13 13:57:35]

lgtm

[pdr., 2013-08-13 16:41:42]

On 2013/08/13 13:57:35, jochen wrote:
> lgtm

LGTM3

[commit-bot: I haz the power, 2013-08-13 16:42:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@sisa.samsung.com/22798002/8001

[commit-bot: I haz the power, 2013-08-13 17:58:09]

Change committed as 156036