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 3852c12e5dd9d5588dd087ef3e51c2e51fa98373..98faf95f34484d9f20ed4b438467df1605378ada 100644
--- a/components/metrics/BUILD.gn
+++ b/components/metrics/BUILD.gn
@@ -95,6 +95,7 @@ static_library("metrics") {
   ]
   deps = [
     ":call_stack_profile_params",
+    ":single_value_histograms",
     "//base",
     "//base:base_static",
     "//components/browser_watcher:stability",
@@ -248,6 +249,22 @@ if (!is_ios) {
   }
 }
 
+source_set("single_value_histograms") {
+  sources = [
+    "single_value_counts_histogram.cc",
+    "single_value_counts_histogram.h",
+    "single_value_histograms_factory_impl.cc",
+    "single_value_histograms_factory_impl.h",
+    "single_value_histograms_provider.cc",
+    "single_value_histograms_provider.h",
+  ]
+
+  deps = [
+    "//components/metrics/public/interfaces:single_value_histograms_mojo_bindings",
+    "//mojo/public/cpp/bindings",
+  ]
+}
+
 source_set("call_stack_profile_params") {
   sources = [
     "call_stack_profile_params.cc",