Adds a Training Manager to the hotword extension.

chrome/browser/resources/hotword/state_manager.js

Index: chrome/browser/resources/hotword/state_manager.js
diff --git a/chrome/browser/resources/hotword/state_manager.js b/chrome/browser/resources/hotword/state_manager.js
index b55dc3dbef6f1296cbc033562ae000ff3e4a5c5c..d5339ce40da894d87d2d73c22a3f3bea0e27c069 100644
--- a/chrome/browser/resources/hotword/state_manager.js
+++ b/chrome/browser/resources/hotword/state_manager.js
@@ -160,6 +160,14 @@ cr.define('hotword', function() {
     },
 
     /**
+     * @return {boolean} True if training is enabled.
+     */
+    isTrainingEnabled: function() {
+      assert(this.hotwordStatus_, 'No hotword status (isTrainingEnabled)');
+      return this.hotwordStatus_.trainingEnabled;
+    },
+
+    /**
      * Callback for hotwordPrivate.getStatus() function.
      * @param {chrome.hotwordPrivate.StatusDetails} status Current hotword
      *     status.
@@ -181,7 +189,9 @@ cr.define('hotword', function() {
       if (!this.hotwordStatus_)
         return;
 
-      if (this.hotwordStatus_.enabled || this.hotwordStatus_.alwaysOnEnabled) {
+      if (this.hotwordStatus_.enabled ||
+          this.hotwordStatus_.alwaysOnEnabled ||
+          this.hotwordStatus_.trainingEnabled) {
         // Start the detector if there's a session, and shut it down if there
         // isn't.
         // NOTE(amistry): With always-on, we want a different behaviour with