AU multi-range fetcher requests properly closed ranges when their length
is known.

* HttpFetcher allows to set the length of data to be fetched.
  LibcurlHttpFetcher uses this value in applying the appropriate libcurl
  option (CURLOPT_RANGE).  MultiHttpFetcher sets the desired payload
  length in the underlying fetcher accordingly.

* Improved functionality of test_http_server: (a) correctly parses
  closed range intervals; (b) generalized response header generation;
  (c) unified and generalized get handling for both stable and flaky
  cases.

* Small scale refactoring, improved logging and readability.

BUG=chromium-os:24666
TEST=unit tests

Change-Id: I1727710ca747088c67a68305f355da683b07b6a3
Reviewed-on: https://gerrit.chromium.org/gerrit/13594
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Commit-Ready: Gilad Arnold <garnold@chromium.org>
diff --git a/update_attempter.cc b/update_attempter.cc
index 7ec14d0..e79f692 100644
--- a/update_attempter.cc
+++ b/update_attempter.cc
@@ -678,10 +678,10 @@
     prefs_->GetInt64(kPrefsUpdateStateNextDataOffset, &next_data_offset);
     uint64_t resume_offset = manifest_metadata_size + next_data_offset;
     if (resume_offset < response_handler_action_->install_plan().size) {
-      fetcher->AddRange(resume_offset, -1);
+      fetcher->AddRange(resume_offset);
     }
   } else {
-    fetcher->AddRange(0, -1);
+    fetcher->AddRange(0);
   }
 }