Revert of [Mac] Remove unnecessary button on 'Bookmark all tabs' window...

Revert of [Mac] Remove unnecessary button on 'Bookmark all tabs' window (patchset #2 id:20001 of https://codereview.chromium.org/583633002/)

Reason for revert:
Nonono you can't just hack out lines from xib files! https://codereview.chromium.org/586543002/ rebuilds the xib file in Xcode to accomplish this and more.

Original issue's description:
> [Mac] Remove unnecessary button on 'Bookmark all tabs' window
>
> Remove unnecessary button on 'Bookmark all tabs' window which appears
> before "Bookmarks Bar"
> XIB Changes:
> Removing the line in the following .xib file which is responsible for the appearance of empty button.
> chrome/app/nibs/BookmarkAllTabs.xib
>
> BUG=415554
> R=asvitkine@chromium.org
>
> TEST=
> 1) Launch chrome, open 2-3 tabs.
> 2) Right click on last tab and select 'Bookmark all tabs'
> 3) Empty button shouldn't be shown.
>
> Committed: https://crrev.com/0ce925fc1ee0f53142313d1b63b32dafbeeeaace
> Cr-Commit-Position: refs/heads/master@{#295714}

TBR=asvitkine@chromium.org,shilpa.shri@samsung.com
NOTREECHECKS=true
NOTRY=true
BUG=415554

Review URL: https://codereview.chromium.org/592833002

Cr-Commit-Position: refs/heads/master@{#295976}

AUTHORS

@@ -402,7 +402,6 @@ ShankarGanesh K <blr.bmlab@gmail.com>
 Shez Baig <sbaig1@bloomberg.net>
 Shiliu Wang <aofdwsl@gmail.com>
 Shiliu Wang <shiliu.wang@intel.com>
-Shilpa Shri <shilpa.shri@samsung.com>
 Shouqun Liu <shouqun.liu@intel.com>
 Shreeram Kushwaha <shreeram.k@samsung.com>
 Shreyas Gopal <shreyas.g@samsung.com>

chrome/app/nibs/BookmarkAllTabs.xib

@@ -832,6 +832,7 @@
 						<reference key="object" ref="607350872"/>
 						<object class="NSMutableArray" key="children">
 							<bool key="EncodedWithXMLCoder">YES</bool>
+							<reference ref="329152418"/>
 							<reference ref="904735886"/>
 							<reference ref="792927203"/>
 							<reference ref="316831958"/>