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/fake_prefs.h b/fake_prefs.h
index 62cf738..240856a 100644
--- a/fake_prefs.h
+++ b/fake_prefs.h
@@ -52,7 +52,7 @@
     PrefValue value;
   };
 
-  // Class to store compile-time type dependant constants.
+  // Class to store compile-time type-dependent constants.
   template<typename T>
   class PrefConsts {
    public: