Add new helper VTTParser::collectDigitsToInt

Add new helper VTTParser::collectDigitsToInt

Since most uses of VTTParser::collectDigits is followed by a call to
String::toInt on the resulting string, add this new helper with the
aim of later removing the temporary string construction.
Handle overflow in the string-to-int conversion by means of saturation.
(The latter is the intended change of semantics.)

Replace uses of collectDigits with collectDigitsToInt where applicable.
After doing this, there remain no callers to collectDigits outside of
VTTParser, so make the function static.

Also move VTTParser::skipWhiteSpace "textually" to group it with the other
'scanning' functions, and make it static since it does not depend on any
VTTParser state.

BUG=305317
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=163098

[Mike West, 2013-12-03 13:55:20]

On 2013/12/03 12:19:41, fs wrote:

LGTM.

It might be worth merging this parsing style with that in
platform/ParsingUtilities.h at some point in the future rather than passing the
whole String around. See Source/core/frame/ContentSecurityPolicy.cpp for some
fiddlings with how that looks in practice.

[Mike West, 2013-12-03 13:55:41]

There was a nit I should have published with the last comment.

https://codereview.chromium.org/101513002/diff/20001/Source/core/html/track/v...
File Source/core/html/track/vtt/VTTRegion.cpp (right):

https://codereview.chromium.org/101513002/diff/20001/Source/core/html/track/v...
Source/core/html/track/vtt/VTTRegion.cpp:262: }
Why did you add the '{' and '}'?

[jochen (gone - plz use gerrit), 2013-12-03 14:48:37]

lgtm

https://codereview.chromium.org/101513002/diff/20001/Source/core/html/track/v...
File Source/core/html/track/vtt/VTTRegion.cpp (right):

https://codereview.chromium.org/101513002/diff/20001/Source/core/html/track/v...
Source/core/html/track/vtt/VTTRegion.cpp:262: }
On 2013/12/03 13:55:41, Mike West wrote:
> Why did you add the '{' and '}'?

So the unsigned position in line 256 is properly scoped I guess

[fs, 2013-12-03 15:51:25]

On 2013/12/03 14:48:37, jochen wrote:
> lgtm
> 
>
https://codereview.chromium.org/101513002/diff/20001/Source/core/html/track/v...
> File Source/core/html/track/vtt/VTTRegion.cpp (right):
> 
>
https://codereview.chromium.org/101513002/diff/20001/Source/core/html/track/v...
> Source/core/html/track/vtt/VTTRegion.cpp:262: }
> On 2013/12/03 13:55:41, Mike West wrote:
> > Why did you add the '{' and '}'?
> 
> So the unsigned position in line 256 is properly scoped I guess

Yes, that.

Thanks for the pointer to platform/ParsingUtilities.h Mike (it's not within
reach quite yet, but hopefully in a while.)

[commit-bot: I haz the power, 2013-12-03 15:51:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/fs@opera.com/101513002/20001

[commit-bot: I haz the power, 2013-12-03 16:55:19]

Change committed as 163098