Bug 1392542 - Update document for new trigger - App Start r=liuche

MozReview-Commit-ID: 48ut6XvuBbg

--HG--
extra : rebase_source : 633b78530348e59bccdbcaf70c6949dc30537375

mobile/android/docs/mma.rst

@@ -142,7 +142,14 @@ List of current Events related data that is sent:
 {
   "event" : "E_Opened_New_Tab"
 }
-
+* App start but Fennec is not set as default browser
+{
+  "event" : "E_Launch_But_Not_Default_Browser"
+}
+* General app start event
+{
+  "event" : "E_Launch_Browser"
+}
 Deep Links:
 Deep links are actions that can point Fennec to open certain pages or load features such as `show bookmark list` or
 `open a SUMO page`. When users see a prompt Leanplum message, they can click the button(s) on it. These buttons can