Add handling to respect role attribute in AXObjects.

Add handling to respect role attribute in AXObjects.

Some AXObjects didn't handle role attribute correctly because it returns
static role for roleValue().
This patch makes they check role attribute on roleValue().
It will have a higher priority than implicit role.
AXObjects handled in this patch:
- AXSlider
- AXProgressIndicator
- AXMenuList
- AXListBoxOption
- AXListBox

BUG=467434
R=dmazzoni

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191899

[je_julie(Not used), 2015-03-16 06:11:49]

je_julie.kim@samsung.com changed reviewers:
+ dmazzoni@chromium.org

[je_julie(Not used), 2015-03-16 06:12:37]

Hi Dominic,

I found we have several problems related to handling role attribute.
1) We don't respect role attribute if we create AXObject other than
AXLayoutObject like AXListBox or AXListBoxOption. Because they returns static
value for roleValue().
2) We can have role attribute even if it is a kind of AXMockObject such as
AXMenuListOption with <Option> tag
but AXMockObject is inherited directly from AXObject and there is no
implementation for attribute handling.
3) AXNodeObject::m_ariaRole is decided with determineAriaRoleAttribute() but
that API is not only for handling role attribute. 
It includes several handling. I think it could cause confusion and we need
another API if we need only to check role attribute.

So, it's hard to handle presentation role correctly because we don't respect
role attribute correctly.
(Actually, it's started from handling presentation role correctly.)

I'd like to fix it step by step.
With this patch, I'd like to make it respect role attribute except AXMockObject.
I could take one of two solutions, one is that if it has explicit role
attribute, it makes AXLayoutObject on AXObjectCacheImpl::createFromRenderer like
AXList::create, it checks role attr, and the other is that I add the code for
handling role attribute on each object like AXTable.
We currently inconsistent solution like AXList and AXTable.
AXList is not created if it has role attribute[1] and AXTable handles role
attribute for itself inside the object[2].

I took the second one with this patch because AX..Objects has some specific
implementation to element.
For instance, AXMenuList adds MenuListPopupRole axobject[3] and it add children
based on dom tree, not layout tree[4].

If blink has a specific reason to keep the current implementation or some
preference for handling it, please let me know.

Additionally,
I removed checking node when AXList is created on
AXObjectCacheImpl::createFromRenderer
because nodeHasRole is checking node and isHTMLXXXElement(*) is checking node as
well.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...
[2]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...
[3]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...
[4]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...
[5]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

Thanks for reading long description.
Please take a look.

[dmazzoni, 2015-03-16 06:17:25]

The CQ bit was checked by dmazzoni@chromium.org

[dmazzoni, 2015-03-16 06:17:26]

lgtm

Great catch! Thanks for writing a clear change description and a good test.

[commit-bot: I haz the power, 2015-03-16 06:17:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1004803004/1

[commit-bot: I haz the power, 2015-03-16 09:04:54]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191899