Add support for single sample metrics.

components/metrics/BUILD.gn

Index: components/metrics/BUILD.gn
diff --git a/components/metrics/BUILD.gn b/components/metrics/BUILD.gn
index cde2219d52612c4f4183cd9c86e30193361c762e..728c347a0662f7976045428549df4137ebb97fe4 100644
--- a/components/metrics/BUILD.gn
+++ b/components/metrics/BUILD.gn
@@ -91,8 +91,11 @@ static_library("metrics") {
   ]
 
   public_deps = [
+    ":single_sample_metrics",
     "//components/metrics/proto",
+    "//components/metrics/public/interfaces:single_sample_metrics_mojo_bindings",
   ]
+
   deps = [
     ":call_stack_profile_params",
     "//base",
@@ -248,6 +251,24 @@ if (!is_ios) {
   }
 }
 
+source_set("single_sample_metrics") {
+  sources = [
+    "single_sample_metrics.cc",
+    "single_sample_metrics.h",
+    "single_sample_metrics_factory_impl.cc",
+    "single_sample_metrics_factory_impl.h",
+  ]
+
+  public_deps = [
+    "//services/service_manager/public/interfaces",
+  ]
+
+  deps = [
+    "//components/metrics/public/interfaces:single_sample_metrics_mojo_bindings",
+    "//mojo/public/cpp/bindings",
+  ]
+}
+
 source_set("call_stack_profile_params") {
   sources = [
     "call_stack_profile_params.cc",
@@ -335,6 +356,7 @@ source_set("unit_tests") {
     "persisted_logs_unittest.cc",
     "profiler/profiler_metrics_provider_unittest.cc",
     "profiler/tracking_synchronizer_unittest.cc",
+    "single_sample_metrics_factory_impl_unittest.cc",
     "stability_metrics_helper_unittest.cc",
     "stability_metrics_provider_unittest.cc",
     "ui/screen_info_metrics_provider_unittest.cc",