Allow obtention of the OS version under Chrome OS

The SysInfo class will provide Chrome OS version from parsing the
LSB_RELEASE file, so call it on Chrome OS too.

Bug: chromium:1012048
Test: Manual
Change-Id: Iba0e3a6d85005a1429f96c0a2d56eea11f8c465f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1848503Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Yves Arrouye <drcrash@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705586}

components/policy/core/common/cloud/cloud_policy_util.cc

@@ -111,7 +111,7 @@ std::string GetMachineName() {
 }
 
 std::string GetOSVersion() {
-#if defined(OS_LINUX) && !defined(OS_CHROMEOS) || defined(OS_MACOSX)
+#if defined(OS_LINUX) || defined(OS_MACOSX)
   return base::SysInfo::OperatingSystemVersion();
 #elif defined(OS_WIN)
   base::win::OSInfo::VersionNumber version_number =