Specify the WebLayer product in the UKM proto.

Bug: 1088488
Change-Id: I9650de41fbc60457ffc7318baf03aa127a52dc5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2253203Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#780390}

components/ukm/ukm_service.cc

@@ -401,6 +401,12 @@ void UkmService::BuildAndStoreLog() {
   report.set_session_id(session_id_);
   report.set_report_id(++report_count_);
 
+  const auto product = static_cast<metrics::ChromeUserMetricsExtension_Product>(
+      client_->GetProduct());
+  // Only set the product if it differs from the default value.
+  if (product != report.product())
+    report.set_product(product);
+
   StoreRecordingsInReport(&report);
 
   metrics::MetricsLog::RecordCoreSystemProfile(client_,