With always-on enabled, always shut down the hotword detector after a trigger.

This is because the hotword stream requires that it be closed and
re-opened after triggering and currently, the only way to do this is to
shutdown the detector since its stream cannot be replaced.

BUG=403138

Review URL: https://codereview.chromium.org/940833002

Cr-Commit-Position: refs/heads/master@{#317023}

chrome/browser/resources/hotword/state_manager.js

@@ -216,7 +216,8 @@ cr.define('hotword', function() {
      */
     isAlwaysOnEnabled: function() {
       assert(this.hotwordStatus_, 'No hotword status (isAlwaysOnEnabled)');
-      return this.hotwordStatus_.alwaysOnEnabled;
+      return this.hotwordStatus_.alwaysOnEnabled &&
+          !this.hotwordStatus_.trainingEnabled;
     },
 
     /**
@@ -485,6 +486,12 @@ cr.define('hotword', function() {
             UmaTriggerSources_[session.source_],
             hotword.constants.UmaTriggerSource.MAX);
       }
+
+      // If we're in always-on mode, shut down the hotword detector. The hotword
+      // stream requires that we close and re-open it after a trigger, and the
+      // only way to accomplish this is to shut everything down.
+      if (this.isAlwaysOnEnabled())
+        this.shutdownDetector_();
     },
 
     /**