Add more components tests to the GN build.

components/domain_reliability/BUILD.gn

Index: components/domain_reliability/BUILD.gn
diff --git a/components/domain_reliability/BUILD.gn b/components/domain_reliability/BUILD.gn
index 528d5d44ddc6c30aab6dd946dcbafab0c217f205..335b1411fcf8c7bd7a2ce5fa689049e90a31d898 100644
--- a/components/domain_reliability/BUILD.gn
+++ b/components/domain_reliability/BUILD.gn
@@ -60,3 +60,22 @@ component("domain_reliability") {
     "//url",
   ]
 }
+
+source_set("unit_tests") {
+  sources = [
+    "config_unittest.cc",
+    "context_unittest.cc",
+    "dispatcher_unittest.cc",
+    "monitor_unittest.cc",
+    "scheduler_unittest.cc",
+    "test_util.cc",
+    "test_util.h",
+    "uploader_unittest.cc",
+    "util_unittest.cc",
+  ]
+
+  deps = [
+    ":domain_reliability",
+    "//testing/gtest",
+  ]
+}