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/multi_range_http_fetcher.h b/multi_range_http_fetcher.h
index 52f0b6f..5b167b2 100644
--- a/multi_range_http_fetcher.h
+++ b/multi_range_http_fetcher.h
@@ -17,7 +17,7 @@
 // This class is a simple wrapper around an HttpFetcher. The client
 // specifies a vector of byte ranges. MultiRangeHttpFetcher will fetch bytes
 // from those offsets, using the same bash fetcher for all ranges. Thus, the
-// fetcher must support beginning a transfter after one has stopped. Pass -1
+// fetcher must support beginning a transfer after one has stopped. Pass -1
 // as a length to specify unlimited length. It really only would make sense
 // for the last range specified to have unlimited length, tho it is legal for
 // other entries to have unlimited length.