Upstream iOS concrete implementation of MetricsHelper class.

BUG=567727

Review URL: https://codereview.chromium.org/1522843002

Cr-Commit-Position: refs/heads/master@{#365015}
diff --git a/ios/chrome/browser/BUILD.gn b/ios/chrome/browser/BUILD.gn
index d743e9b8..2f51f237 100644
--- a/ios/chrome/browser/BUILD.gn
+++ b/ios/chrome/browser/BUILD.gn
@@ -195,6 +195,8 @@
     "install_time_util.mm",
     "installation_notifier.h",
     "installation_notifier.mm",
+    "interstitials/ios_chrome_metrics_helper.cc",
+    "interstitials/ios_chrome_metrics_helper.h",
     "invalidation/ios_chrome_profile_invalidation_provider_factory.cc",
     "invalidation/ios_chrome_profile_invalidation_provider_factory.h",
     "ios_chrome_field_trials.cc",
@@ -513,6 +515,7 @@
     "//components/resources",
     "//components/search",
     "//components/search_engines",
+    "//components/security_interstitials/core",
     "//components/sessions",
     "//components/signin/core/browser",
     "//components/signin/core/common",