Rename ElementData's attribute related methods for clarity

Rename ElementData's attribute related methods for clarity

Rename ElementData's attribute related methods for clarity:
* length() -> attributeCount()
* isEmpty() -> hasAttributes()
* getAttributeItem(name) -> findAttributeByName(name)
* attributeItem(index) -> attributeAt(index)
* getAttributeItemIndex(name) -> findAttributeIndexByName(name)
* addAttribute(name, value) -> appendAttribute(name, value)
* removeAttribute(index) -> removeAttributeAt(index)

This is inpired by the following WebKit revision by benjamin@webkit.org:
http://trac.webkit.org/changeset/162394

R=esprehn@chromium.org, adamk@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175611

[esprehn, 2014-06-05 20:45:34]

lgtm

[commit-bot: I haz the power, 2014-06-05 20:46:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/313973003/1

[commit-bot: I haz the power, 2014-06-05 20:48:47]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  blink_presubmit on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/7065)
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/1...)

[commit-bot: I haz the power, 2014-06-05 20:51:11]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-06-05 20:51:13]

Try jobs failed on following builders:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)

[Inactive, 2014-06-05 20:53:12]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-06-05 20:54:11]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/313973003/1

[commit-bot: I haz the power, 2014-06-05 20:56:43]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  blink_presubmit on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/7070)
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/1...)

[commit-bot: I haz the power, 2014-06-05 20:58:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-06-05 20:58:37]

Try jobs failed on following builders:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)

[Inactive, 2014-06-05 23:16:03]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-06-05 23:16:21]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/313973003/1

[commit-bot: I haz the power, 2014-06-06 00:29:22]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/1...)

[commit-bot: I haz the power, 2014-06-06 00:55:52]

Change committed as 175611