MD Settings: settings-dropdown-menu, restore "Enter" key behavior.

chrome/browser/resources/settings/controls/settings_dropdown_menu.html

Index: chrome/browser/resources/settings/controls/settings_dropdown_menu.html
diff --git a/chrome/browser/resources/settings/controls/settings_dropdown_menu.html b/chrome/browser/resources/settings/controls/settings_dropdown_menu.html
index 89654d12163039c555dfccf322e13019838bcfb1..cb09d77dd98ea1965deb8e4a214d5a8f726df55c 100644
--- a/chrome/browser/resources/settings/controls/settings_dropdown_menu.html
+++ b/chrome/browser/resources/settings/controls/settings_dropdown_menu.html
@@ -18,15 +18,15 @@
         <template is="dom-repeat" items="[[menuOptions]]" initial-count="5">
           <!--TODO(dpapad): Use <button class="paper-item">..</button> once it
               lands in paper-item-shared-styles.html-->
-          <div class="dropdown-item" role="option" data-value$="[[item.value]]">
+          <button class="dropdown-item" role="option" data-value$="[[item.value]]">

[stevenjb, 2016/07/12 22:46:57]

Should we change to button for all paper-dropdown-menu cases? Maybe not in this
CL, but it would be good to use a consistent pattern.

Also, my understanding is that <div> is considerably cheaper than <button>, I
assume there isn't an easy way to decorate the <div> to get the behavior we
want?

[dpapad, 2016/07/12 22:56:09]

I agree that we should change it to something that works for all
paper-dropdown-menus, I am just addressing settings-dropdown-menu only in this
CL.

Regarding performance, my measurements showed that both <button> and <div> are
much faster than <paper-item>. I did not observe a noticeable difference in
performance between <div> and <button>.

[Dan Beam, 2016/07/12 23:00:27]

80 col wrap

[dpapad, 2016/07/12 23:18:02]

Done.

[michaelpg, 2016/07/12 23:44:22]

wrap

[dpapad, 2016/07/13 01:01:07]

Already done.

             [[item.name]]
-          </div>
+          </button>
         </template>
-        <div class="dropdown-item" role="option"
+        <button class="dropdown-item" role="option"
             data-value$="[[notFoundValue_]]"
             hidden$="[[!isSelectedNotFound_(selected_)]]">
           $i18n{custom}
-        </div>
+        </button>
       </paper-listbox>
     </paper-dropdown-menu>
   </template>