metrics: add support for other product id

metrics_uploader should use the GOOGLE_METRICS_PRODUCT_ID field from os-release
whenever possible instead of the default Chrome product id.

BUG=chromium:415744
TEST=FEATURES=test emerge-gizmo metrics succeeds.
TEST=test_that platform_MetricsUploader succeeds.

CQ-DEPEND=CL:221963

Change-Id: I69b1a6ca766048ad80d93008a2fe3b18879bf1da
Reviewed-on: https://chromium-review.googlesource.com/221953
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
diff --git a/metrics/metrics_daemon.h b/metrics/metrics_daemon.h
index 07072f9..7c7f8d2 100644
--- a/metrics/metrics_daemon.h
+++ b/metrics/metrics_daemon.h
@@ -39,7 +39,8 @@
             const std::string& scaling_max_freq_path,
             int upload_interval_secs,
             const std::string& server,
-            const std::string& metrics_file);
+            const std::string& metrics_file,
+            const std::string& config_root);
 
   // Does all the work. If |run_as_daemon| is true, daemonizes by
   // forking.
@@ -300,6 +301,9 @@
   // Test mode.
   bool testing_;
 
+  // Root of the configuration files to use.
+  std::string config_root_;
+
   // The metrics library handle.
   MetricsLibraryInterface* metrics_lib_;