Fix broken clockstate.network2 histogram and add unit test

components/network_time/BUILD.gn

Index: components/network_time/BUILD.gn
diff --git a/components/network_time/BUILD.gn b/components/network_time/BUILD.gn
index c7170edd004172cbdc6304f699f5f2ccc67302da..11e5c6630e06f87d8924c9df877bd229da0bed08 100644
--- a/components/network_time/BUILD.gn
+++ b/components/network_time/BUILD.gn
@@ -28,6 +28,7 @@ source_set("unit_tests") {
 
   deps = [
     ":network_time",
+    ":network_time_test_support",
     "//base",
     "//base/test:test_support",
     "//components/client_update_protocol",
@@ -38,3 +39,18 @@ source_set("unit_tests") {
     "//testing/gtest",
   ]
 }
+
+source_set("network_time_test_support") {
+  testonly = true
+  sources = [
+    "network_time_test_utils.cc",
+    "network_time_test_utils.h",
+  ]
+
+  deps = [
+    "//base",
+    "//base/test:test_support",
+    "//components/variations",
+    "//testing/gtest",
+  ]
+}