Don't insert redundant BR for merging

This patch changes delete selection process not to insert redundant BR element for merging.

* editing/deleting/delete-br-001.html:
 This patch keeps origin BRs.
* editing/deleting/delete-before-block-image-2-expected.txt
 This patch keeps an origin IMG element rather than inserting new one.
* editing/deleting/delete-br-001.html
  This patch keeps original BR elements rather than removing BR then inserting BR again.
* editing/deleting/delete-br-after-image.html
 This patch adds a new test described in issue report.
* editing/deleting/delete-inline-br.html
 Imported from http://trac.webkit.org/changeset/154479 
* editing/inserting/font-size-clears-from-typing-style-expected.txt
 This patch doesn't causes redundant block, DIV, merging. 


BUG=173835, 235742
R=eseidel@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=157505

[yosin_UTC9, 2013-07-10 09:08:58]

Hi,
Could you review this patch?
Thanks in advance.

[ojan, 2013-07-11 23:50:06]

I really don't know this code well enough to know if the change is correct.
Eric, Levi?

[yosin_UTC9, 2013-07-25 01:28:48]

ping...

[yosin_UTC9, 2013-09-05 07:25:33]

Levi...

It seems this patch covers more cases than
https://codereview.chromium.org/23311004/

[eseidel, 2013-09-09 20:30:33]

lgtm

I'm willing to bet that Yosin will know this code better than any of us in a
very short while (probably already does).

I'm just hear to grease the wheels.

[commit-bot: I haz the power, 2013-09-09 20:30:44]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/yosin@chromium.org/18799004/17001

[leviw_travelin_and_unemployed, 2013-09-09 20:32:29]

On 2013/09/09 20:30:33, eseidel wrote:
> lgtm
> 
> I'm willing to bet that Yosin will know this code better than any of us in a
> very short while (probably already does).
> 
> I'm just hear to grease the wheels.

Thanks for getting to these reviews, Eric. I'm sure you're right re: Yosin's
knowledge :)

[commit-bot: I haz the power, 2013-09-09 22:53:22]

Retried try job too often on win_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_blink_...

[yosin_UTC9, 2013-09-10 05:48:43]

Committed patchset #2 manually as r157505 (presubmit successful).