[DNS] Don't adjust the scroll position if the anchor element changes in size

Don't adjust the scroll position if the anchor element changes in size

https://crrev.com/1755923002 added logic to pick a corner of the anchor candidate
from which the relative offset would be calculated. Even if the anchor element itself
changed in height (during restore), the scroll position would be adjusted accordingly.
This breaks for cases like crbug.com/600891 where the content is added to the anchor
node and adjusting the scroll to compensate for the change is not the right thing to
do.

Note that the logic above was added with a bunch of other changes and it's not clear 
whether or not it was done to fix any existing bugs. i.e. we may need to revisit
the changes in this CL if we find that it doesn't work in some cases.

BUG=600891

[ymalik, 2016-04-12 18:54:50]

Description was changed from

==========
[WIP] Don't select an anchor that my change due to a layout.

BUG=600891
==========

to

==========
Don't adjust the scroll position if the anchor element changes in size

https://crrev.com/1755923002.

BUG=600891
==========

[ymalik, 2016-04-12 20:11:50]

Description was changed from

==========
Don't adjust the scroll position if the anchor element changes in size

https://crrev.com/1755923002.

BUG=600891
==========

to

==========
Don't adjust the scroll position if the anchor element changes in size

https://crrev.com/1755923002 added logic to pick a corner of the anchor
candidate
from which the relative offset would be calculated. Even if the anchor element
itself
changed in height (during restore), the scroll position would be adjusted
accordingly.
This breaks for cases like crbug.com/600891 where the content is added to the
anchor
node and adjusting the scroll to compensate for the change is not the right
thing to
do.

Note that the logic above was added with a bunch of other changes and it's not
clear 
whether or not it was done to fix any existing bugs. i.e. we may need to revisit
the changes in this CL if we find that it doesn't work in some cases.

BUG=600891
==========

[ymalik, 2016-04-12 20:11:50]

ymalik@chromium.org changed reviewers:
+ ojan@chromium.org

[ymalik, 2016-04-12 20:13:44]

@ojan, PTAL :)

[ojan, 2016-04-13 17:50:11]

I think we should wait until skobes is back from vacation. I suspect that this
is working around the fact that our current anchoring algorithm is wrong. It'll
be hard to know if this is a good change until we have a good understanding of
what the anchoring algorithm should be.

[ymalik, 2016-05-12 22:35:56]

ymalik@chromium.org changed reviewers:
- ojan@chromium.org