Changes the dummy-disable-background-switch flag to be lowercase.

base::CommandLine will DCHECK if it sees a flag with uppercase letters.

BUG=None
TEST=None

Review URL: https://codereview.chromium.org/1452823009

Cr-Commit-Position: refs/heads/master@{#360590}

ios/chrome/browser/metrics/ios_chrome_metrics_services_manager_client.cc

@@ -56,7 +56,7 @@ IOSChromeMetricsServicesManagerClient::CreateVariationsService() {
   // networking.
   return variations::VariationsService::Create(
       make_scoped_ptr(new IOSChromeVariationsServiceClient), local_state_,
-      GetMetricsStateManager(), "dummyDisableBackgroundSwitch",
+      GetMetricsStateManager(), "dummy-disable-background-switch",
       ::CreateUIStringOverrider());
 }