Update input[type=range]'s step base handling to match spec.

Update input[type=range]'s step base handling to match spec.

The HTML spec recently shifted to using 'value' as the first fallback
option for an input element's "step base" (if no 'min' attribute),

 http://www.whatwg.org/specs/web-apps/current-work/#concept-input-min-zero

Also bring type=range elements into line with that, including using
that step base when clamping values to the supported range.

R=
BUG=339194
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166367

[sof, 2014-02-03 16:42:56]

When you have a moment, please take a look.

Came across some issues with stepUp()/stepDown() while looking at this;
addressing that separately. But, other than that, this aligns behavior with spec
+ Gecko.

[sof, 2014-02-03 18:36:08]

https://codereview.chromium.org/152753002/diff/1/Source/core/html/forms/Range...
File Source/core/html/forms/RangeInputType.cpp (left):

https://codereview.chromium.org/152753002/diff/1/Source/core/html/forms/Range...
Source/core/html/forms/RangeInputType.cpp:130: const AtomicString&
precisionValue = element().fastGetAttribute(precisionAttr);
I see there's a use counter against this attribute (and has been for a while);
anyone know (or know who I should ask? :) ) what numbers are being reported?

[tkent, 2014-02-04 00:49:56]

lgtm

https://codereview.chromium.org/152753002/diff/1/Source/core/html/forms/Range...
File Source/core/html/forms/RangeInputType.cpp (left):

https://codereview.chromium.org/152753002/diff/1/Source/core/html/forms/Range...
Source/core/html/forms/RangeInputType.cpp:130: const AtomicString&
precisionValue = element().fastGetAttribute(precisionAttr);
On 2014/02/03 18:36:09, sof wrote:
> I see there's a use counter against this attribute (and has been for a while);
> anyone know (or know who I should ask? :) ) what numbers are being reported?

I checked it in the last week, and found the number was unexpectedly high.

[commit-bot: I haz the power, 2014-02-04 00:50:07]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sigbjornf@opera.com/152753002/1

[sof, 2014-02-04 06:26:42]

https://codereview.chromium.org/152753002/diff/1/Source/core/html/forms/Range...
File Source/core/html/forms/RangeInputType.cpp (left):

https://codereview.chromium.org/152753002/diff/1/Source/core/html/forms/Range...
Source/core/html/forms/RangeInputType.cpp:130: const AtomicString&
precisionValue = element().fastGetAttribute(precisionAttr);
On 2014/02/04 00:49:56, tkent wrote:
> On 2014/02/03 18:36:09, sof wrote:
> > I see there's a use counter against this attribute (and has been for a
while);
> > anyone know (or know who I should ask? :) ) what numbers are being reported?
> 
> I checked it in the last week, and found the number was unexpectedly high.

Thanks; how curious.

[commit-bot: I haz the power, 2014-02-04 08:05:09]

Change committed as 166367