update_engine: fixed remaining linter and some spelling errors

Fixed remaining errors from cpplint as well as some spelling errors
mostly in comments.

BUG=None
TEST=FEATURES=test emerge-link update_engine

Change-Id: I484988ab846ac5a3c68c016ddccfb247f225ec27
Reviewed-on: https://chromium-review.googlesource.com/208897
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/update_manager/event_loop.h b/update_manager/event_loop.h
index 129761c..c639f88 100644
--- a/update_manager/event_loop.h
+++ b/update_manager/event_loop.h
@@ -18,7 +18,7 @@
 
 typedef guint EventId;
 
-// A null EventId doesn't idenify any valid event.
+// A null EventId doesn't identify any valid event.
 static constexpr EventId kEventIdNull = 0;
 
 // Schedules the passed |callback| to run from the GLib's main loop after a