Transmit a X-Chrome-UMA-Enabled bit to Google domains from clients that have UMA enabled.

chrome/browser/metrics/metrics_service.h

Index: chrome/browser/metrics/metrics_service.h
diff --git a/chrome/browser/metrics/metrics_service.h b/chrome/browser/metrics/metrics_service.h
index ff4df36914c23d3a93c8bd18e0ce74181a0972cd..510b69743c129fa41f3cf07f7cefc07ecf0d5adb 100644
--- a/chrome/browser/metrics/metrics_service.h
+++ b/chrome/browser/metrics/metrics_service.h
@@ -32,6 +32,7 @@
 
 class BookmarkModel;
 class BookmarkNode;
+class ChromeNetworkDelegate;
 class MetricsReportingScheduler;
 class PrefService;
 class Profile;
@@ -437,6 +438,7 @@ class MetricsServiceHelper {
   friend class InstantFieldTrial;
   friend bool prerender::IsOmniboxEnabled(Profile* profile);
   friend class extensions::ExtensionDownloader;
+  friend class ChromeNetworkDelegate;
 
   // Returns true if prefs::kMetricsReportingEnabled is set.
   static bool IsMetricsReportingEnabled();