Add a tray notification UI for speech input recording in the extension API.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 0e4dfad18540240636bc12d99fed4004b921d9b4..1bc3ac2736c22e12ab1bb99c02056766f7316e2a 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -628,6 +628,11 @@ const char kEnableAutoSpellCorrect[] = "browser.enable_autospellcorrect";
 const char kSpeechInputFilterProfanities[] =
     "browser.speechinput_censor_results";
 
+// Boolean pref to determine if the tray notification balloon for speech input
+// extension API has been already shown once to the user.
+const char kSpeechInputTrayNotificationShown[] =
+    "browser.speechinput_tray_notification_shown";
+
 // Boolean controlling whether history saving is disabled.
 const char kSavingBrowserHistoryDisabled[] = "history.saving_disabled";