MD Settings: in spell-check page, disable add button when input is empty.

chrome/browser/resources/settings/languages_page/edit_dictionary_page.js

Index: chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
diff --git a/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js b/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
index 7dc1b199e61562f06e01337242f5b6bd1fbc4d33..421e78056ef2aadfda373c505ada3e9ee8c781a6 100644
--- a/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
+++ b/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
@@ -10,6 +10,9 @@ Polymer({
   is: 'settings-edit-dictionary-page',
 
   properties: {
+    /** @private {string} */
+    newWordValue_: String,
+
     /** @private {!Array<string>} */
     words_: {
       type: Array,
@@ -32,6 +35,16 @@ Polymer({
   },
 
   /**
+   * Check if the new word text-field is empty.
+   * @private
+   * @param {string} value
+   * @return {boolean} true if value is empty, false otherwise.
+   */
+  validateWord_: function(value) {
+    return !!value.trim();
+  },
+
+  /**
    * Handles updates to the word list. Additions triggered by this element are
    * de-duped so the word list remains a set. Words are appended to the end
    * instead of re-sorting the list so it's clear what words were added.
@@ -82,8 +95,8 @@ Polymer({
    */
   addWordFromInput_: function() {
     // Spaces are allowed, but removing leading and trailing whitespace.
-    var word = this.$.newWord.value.trim();
-    this.$.newWord.value = '';
+    var word = this.newWordValue_.trim();
+    this.newWordValue_ = '';
     if (!word)
       return;