MD Settings: Checks the event target in the language tap event handler

chrome/browser/resources/settings/languages_page/languages_page.html

 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-collapse/iron-collapse.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_expand_button/cr_expand_button.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
@@ skipping 60 matching lines @@
                   [[item.language.displayName]]
                 </div>
                 <div class="middle">
                   <iron-icon icon="settings:done"
                       hidden$="[[!isProspectiveUILanguage_(
                           item.language.code, prefs.intl.app_locale.value)]]">
                   </iron-icon>
                 </div>
 </if>
                 <paper-icon-button id="more-[[item.language.code]]"
-                    icon="cr:more-vert" toggles
+                    icon="cr:more-vert" toggles class="dropdown-trigger"
                     active="{{item.optionsMenuOpened}}">

[Dan Beam, 2016/08/10 20:45:26]

can't we just make an on-tap=methodThatCallsEventStopPropagation?

[Moe, 2016/08/10 23:58:32]

the event could originate from either of dropdown-(trigger|content|item)
depending on where the user taps. We would need three on-tap handlers.

[Dan Beam, 2016/08/12 01:43:43]

could you put the <iron-dropdown> in the <paper-icon-button> to fix this?

[Moe, 2016/08/12 16:46:53]

I tried, but couldn't get the dropdown to show :(

                 </paper-icon-button>
                 <iron-dropdown opened="{{item.optionsMenuOpened}}"
                     horizontal-align="right" vertical-align="auto">
                   <div class="dropdown-content">
                     <button class="dropdown-item" role="option"
                         on-tap="onMoveUpTap_"
                         hidden="[[isFirstLanguage_(index,
                                                    languages.enabled.*)]]">
                       $i18n{moveUp}
                     </button>
@@ skipping 124 matching lines @@
             associated-control="[[$$('#spellcheck-subpage-trigger')]]"
             page-title="$i18n{editDictionaryPageTitle}">
           <settings-edit-dictionary-page></settings-edit-dictionary-page>
         </settings-subpage>
       </template>
 </if>
     </settings-animated-pages>
   </template>
   <script src="languages_page.js"></script>
 </dom-module>