Start and stop the hotword detector when the user opens/closes the launcher.

chrome/browser/resources/hotword/constants.js

Index: chrome/browser/resources/hotword/constants.js
diff --git a/chrome/browser/resources/hotword/constants.js b/chrome/browser/resources/hotword/constants.js
index 2aab1ed79f621055f0c26e8cf051bf1fa447750a..304f6cf3c8b234313f6acf0f5dce6d7c148558b6 100644
--- a/chrome/browser/resources/hotword/constants.js
+++ b/chrome/browser/resources/hotword/constants.js
@@ -82,6 +82,17 @@ var NaClPlugin = {
 
 
 /**
+ * Source of a hotwording session request.
+ * @enum {string}
+ */
+var SessionSource = {
+  LAUNCHER: 'launcher',
+  NTP: 'ntp',
+  GOOGLE_COM: 'google.com'

[rpetterson, 2014/09/10 17:53:31]

Where are the NTP and GOOGLE_COM ones currently (or will be) used?

[Anand Mistry (off Chromium), 2014/09/10 23:29:42]

They're not used in this change, so I've removed them and will add them back
when I need to. They will be used when I do the google.com/ntp integration.

+};
+
+
+/**
  * The browser UI language.
  * @const {string}
  */
@@ -96,6 +107,7 @@ return {
   Error: Error,
   Event: Event,
   NaClPlugin: NaClPlugin,
+  SessionSource: SessionSource,
   UI_LANGUAGE: UI_LANGUAGE
 };