[NTP] Adding a left span for custom links edit html

When changing the font size on the settings, changing on the remove
button is different than changing on the right span container for the
other two buttons, that's why we see the inconsistent behavior.
Therefore, adding additional left span for the remove button.

Screencast:
https://screencast.googleplex.com/cast/NDkxMzQ4OTQ4NzMzMTMyOHw5N2Y4MzQzMS0yYQ

Bug: 883192
Change-Id: I398402cfdec9d8a93e95802fb4d99f6ded552cd0
Reviewed-on: https://chromium-review.googlesource.com/1255612
Commit-Queue: Weilun Shi <sweilun@chromium.org>
Reviewed-by: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595670}

chrome/browser/resources/local_ntp/custom_links_edit.css

@@ -128,9 +128,6 @@ input:focus + .underline {
   margin-top: 24px;
 }
 
-.buttons-container .right {
-}
-
 button {
   border: none;
   border-radius: 4px;

chrome/browser/resources/local_ntp/custom_links_edit.html

@@ -31,8 +31,10 @@
         <div id="invalid-url" class="error-msg"></div>
       </div>
       <div class="buttons-container">
+        <span>
           <button id="delete" class="secondary" type="button" tabindex="0"></button>
-        <span class="right">
+        </span>
+        <span>
           <button id="cancel" class="secondary" type="button" tabindex="0"></button>
           <button type="submit" id="done" class="primary" tabindex="0"></button>
         </span>