Bug 778296 (previous commit was empty!) - Add comment about thread-safety to nsITimer DONTBUILD. r=bz

xpcom/threads/nsITimer.idl

@@ -52,6 +52,12 @@ interface nsITimerCallback : nsISupports
  * documented below.  You may also re-initialize (using one of the init()
  * methods) an existing instance to avoid the overhead of destroying and
  * creating a timer.  It is not necessary to cancel the timer in that case.
+ *
+ * It is not currently safe to initialize timers on any thread other than the
+ * main thread (it will cause races on the timers' delay adjustment mechanism,
+ * which may mess up timings).   You can, however, cancel() and/or release a
+ * timer on a non-main thread (provided that its callback object has a
+ * thread-safe release() function).
  */
 [scriptable, uuid(193fc37a-8aa4-4d29-aa57-1acd87c26b66)]
 interface nsITimer : nsISupports