scrollTop and scrollLeft always 0 in DOMContentLoaded handler on a scrolled page

scrollTop and scrollLeft always 0 in DOMContentLoaded handler on a scrolled page

Currently, when performing a "back" navigation, the scroll position
is restored at the time the first layout happens (see FrameLoader::didFirstLayout).
If that does not go through, another attempt to restore the scroll position
is made when the frame completes loading (see FrameLoader::checkLoadCompleteForThisFrame).

In a closer look, one might notice that in the later, not only the "back" navigation
case is covered, but also "reload".

Patch makes these two attempts of restore the scroll position to operate under the
same circumstances: back and reload.

Apart from bringing them in pair, it also makes it possible to query the scroll
position at the time DOMContentLoaded fires, as Gecko and Presto engines do.

Test: fast/loader/scroll-position-restored-on-reload-at-load-event.html
        fast/loader/scroll-position-restored-on-back-at-load-event.html
R=Nate Chapin
BUG=290895
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=161098

[Nate Chapin, 2013-10-30 19:00:44]

lgtm

https://codereview.chromium.org/52893003/diff/1/Source/core/loader/FrameLoade...
File Source/core/loader/FrameLoader.cpp (right):

https://codereview.chromium.org/52893003/diff/1/Source/core/loader/FrameLoade...
Source/core/loader/FrameLoader.cpp:1045: && (isBackForwardLoadType(m_loadType)
|| m_loadType == FrameLoadTypeReload || m_loadType ==
FrameLoadTypeReloadFromOrigin))
It might be good to split this into 2 separate if() statements for readability -
an early exit if there is no page, and a check that m_loadType is one of the
desired values.

[commit-bot: I haz the power, 2013-10-31 20:49:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/a1.gomes@sisa.samsung.com/52893003/70001

[commit-bot: I haz the power, 2013-10-31 22:14:29]

Change committed as 161098