Move pre_read_field_trial_utils.h/cc to common/.

components/startup_metric_utils/common/BUILD.gn

Index: components/startup_metric_utils/common/BUILD.gn
diff --git a/components/startup_metric_utils/common/BUILD.gn b/components/startup_metric_utils/common/BUILD.gn
index bfcb358e879795fe682ab6fe2953f9fec68852eb..d9b2f0996e79ea5fee4a73ed06d09b241d90085a 100644
--- a/components/startup_metric_utils/common/BUILD.gn
+++ b/components/startup_metric_utils/common/BUILD.gn
@@ -4,6 +4,8 @@
 
 source_set("common") {
   sources = [
+    "pre_read_field_trial_utils_win.cc",
+    "pre_read_field_trial_utils_win.h",
     "startup_metric_message_generator.cc",
     "startup_metric_message_generator.h",
     "startup_metric_messages.h",
@@ -11,6 +13,7 @@ source_set("common") {
 
   deps = [
     "//base",
+    "//components/variations",
     "//ipc",
   ]
 }