Revert "update_engine: Support milestones to EOL from Omaha"

This reverts commit 893cae4b0e5141bcaf9f56b1775e681c8f523630.

Reason for revert: use of EOL date and EOL notification date instead milestones to EOL.

Original change's description:
> update_engine: Support milestones to EOL from Omaha
>
> Initiative to show EOL message on Chrome OS devices require that
> update_engine parses the fields within Omaha response that pertain to the
> new milestones to EOL field. The Omaha response will include a new
> field called "milestones_to_eol" which will be an integer value
> string.
>
> The job of update_engine when it comes to milestones to EOL from Omaha
> is to merely forward. No checks and no modifications of fields are
> done within update_engine besides being able to convert the milestones
> to EOL from a string to integer.
>
> BUG=chromium:994999
> TEST=FEATURES="test" emerge-$BOARD update_engine update_engine-client
> TEST=cros deploy $IP update_engine update_engine-client
> TEST=test_that -b $BOARD $IP autoupdate_EOL # from Cq-Depend
> TEST=test_that -b $BOARD $IP autoupdate_EOL.milestones # from Cq-Depend
>
> Cq-Depend:chromium:1761371
> Change-Id: I268e4c8e641b17d6a727a50f53285cc97c76eb22
> Reviewed-on: https://chromium-review.googlesource.com/1759285
> Tested-by: Jae Hoon Kim <kimjae@chromium.org>
> Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
> Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
> Reviewed-by: Nicolas Norvez <norvez@chromium.org>
> Reviewed-by: Amin Hassani <ahassani@chromium.org>

TBR=maybelle@chromium.org,norvez@chromium.org,ahassani@chromium.org,abutzier@chromium.org,chromiumos-cl-exonerator@appspot.gserviceaccount.com,kimjae@chromium.org

BUG=chromium:994999
TEST=none
Cq-Depend:chromium:1782971
Change-Id: I42e75e22948b3653500d355027dc3312015c9ebf
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/1782970
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/omaha_utils.cc b/omaha_utils.cc
index dffa5d3..6bd7525 100644
--- a/omaha_utils.cc
+++ b/omaha_utils.cc
@@ -17,15 +17,17 @@
 #include "update_engine/omaha_utils.h"
 
 #include <base/logging.h>
-#include <base/strings/string_number_conversions.h>
 
 namespace chromeos_update_engine {
 
+namespace {
+
+// The possible string values for the end-of-life status.
 const char kEolStatusSupported[] = "supported";
 const char kEolStatusSecurityOnly[] = "security-only";
 const char kEolStatusEol[] = "eol";
 
-const MilestonesToEol kMilestonesToEolNone = -1;
+}  // namespace
 
 const char* EolStatusToString(EolStatus eol_status) {
   switch (eol_status) {
@@ -48,23 +50,8 @@
     return EolStatus::kSecurityOnly;
   if (eol_status == kEolStatusEol)
     return EolStatus::kEol;
-  LOG(WARNING) << "Invalid EOL attribute: " << eol_status;
+  LOG(WARNING) << "Invalid end-of-life attribute: " << eol_status;
   return EolStatus::kSupported;
 }
 
-std::string MilestonesToEolToString(MilestonesToEol milestones_to_eol) {
-  return base::IntToString(milestones_to_eol);
-}
-
-MilestonesToEol StringToMilestonesToEol(const std::string& milestones_to_eol) {
-  MilestonesToEol milestone = kMilestonesToEolNone;
-  if (!base::StringToInt(milestones_to_eol, &milestone)) {
-    LOG(WARNING) << "Invalid milestones to EOL attribute: "
-                 << milestones_to_eol;
-    return kMilestonesToEolNone;
-  }
-
-  return milestone;
-}
-
 }  // namespace chromeos_update_engine