Move ChromeOS hardware class init out of MetricsService.

chrome/browser/metrics/metrics_log.cc

Index: chrome/browser/metrics/metrics_log.cc
diff --git a/chrome/browser/metrics/metrics_log.cc b/chrome/browser/metrics/metrics_log.cc
index bd90025b7b109e04f84bcbf51ec93373f26821d6..f0ba00a920055737e591c508f19c33f026b6b7ae 100644
--- a/chrome/browser/metrics/metrics_log.cc
+++ b/chrome/browser/metrics/metrics_log.cc
@@ -336,6 +336,10 @@ void MetricsLog::RecordEnvironment(
   system_profile->set_application_locale(client_->GetApplicationLocale());
 
   SystemProfileProto::Hardware* hardware = system_profile->mutable_hardware();
+
+  // By default, the hardware class is empty (i.e., unknown).
+  hardware->set_hardware_class(std::string());
+
   hardware->set_cpu_architecture(base::SysInfo::OperatingSystemArchitecture());
   hardware->set_system_ram_mb(base::SysInfo::AmountOfPhysicalMemoryMB());
 #if defined(OS_WIN)