Make single_sample_metrics into its own target

components/metrics/BUILD.gn

Index: components/metrics/BUILD.gn
diff --git a/components/metrics/BUILD.gn b/components/metrics/BUILD.gn
index 1f18b9346d20b8b1861d25e65182dc058d8a646e..105572559b71aafbcf48b9d6b0a125c83a65081c 100644
--- a/components/metrics/BUILD.gn
+++ b/components/metrics/BUILD.gn
@@ -91,9 +91,7 @@ static_library("metrics") {
   ]
 
   public_deps = [
-    ":single_sample_metrics",
     "//components/metrics/proto",
-    "//components/metrics/public/interfaces:single_sample_metrics_mojo_bindings",
   ]
 
   deps = [
@@ -250,7 +248,7 @@ if (!is_ios) {
   }
 }
 
-source_set("single_sample_metrics") {
+static_library("single_sample_metrics") {
   sources = [
     "single_sample_metrics.cc",
     "single_sample_metrics.h",
@@ -259,11 +257,14 @@ source_set("single_sample_metrics") {
   ]
 
   deps = [
-    "//components/metrics/public/interfaces:single_sample_metrics_mojo_bindings",
     "//mojo/public/cpp/bindings",
     "//services/service_manager/public/cpp",
     "//services/service_manager/public/interfaces",
   ]
+
+  public_deps = [
+    "//components/metrics/public/interfaces:single_sample_metrics_mojo_bindings",
+  ]
 }
 
 source_set("call_stack_profile_params") {
@@ -365,6 +366,7 @@ source_set("unit_tests") {
     ":metrics",
     ":net",
     ":profiler",
+    ":single_sample_metrics",
     ":test_support",
     ":ui",
     "//base/test:test_support",