Revert of Remove style spans to follow the styles of the block element (patchset #2 id:20001 of https://codereview.chromium.org/2102913002/ )

Reason for revert:
Assignment within conditional on line 836 of ReplaceSelectionCommand.cpp is breaking Win8 build:

https://build.chromium.org/p/chromium.win/builders/Win8%20GYP%20%28dbg%29/builds/133

crbug.com/624263 tracks build failures

Original issue's description:
> Remove style spans to follow the styles of the block element
>
> This CL removes style spans to follow the styles of the block
> element(li, pre, td, and h1~6) when the text of the pasted
> or merged element becomes a part of the block element.
>
> BUG=226941
> TEST=third_party/WebKit/LayoutTests/editing/deleting/backspace-merge-into-block-element.html
>
> Committed: https://crrev.com/5220699381aae450f22d1ea3805141deb139f8f3
> Cr-Commit-Position: refs/heads/master@{#402659}

TBR=yosin@chromium.org,joone.hur@intel.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=226941

Review-Url: https://codereview.chromium.org/2109973002
Cr-Commit-Position: refs/heads/master@{#402696}
(cherry picked from commit 45859e627709ac2a56e939a00f725a0fca27f75f)

Review-Url: https://codereview.chromium.org/2111473002
Cr-Commit-Position: refs/branch-heads/2783@{#2}
Cr-Branched-From: 956d75c97da94022381b07c336a4c258b04fb8bc-refs/heads/master@{#402676}
4 files changed