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

chrome/browser/profiles/profile_impl_io_data.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/profiles/profile_impl_io_data.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 95 matching lines @@
 
   if (!main_request_context_getter_) {
     main_request_context_getter_ =
         ChromeURLRequestContextGetter::CreateOriginal(
             profile_, io_data_);
   }
   io_data_->predictor_->InitNetworkPredictor(profile_->GetPrefs(),
                                              local_state,
                                              io_thread,
                                              main_request_context_getter_);
+
+  io_data_->enable_metrics()->Init(prefs::kMetricsReportingEnabled,
+                                   local_state, NULL);
+  io_data_->enable_metrics()->MoveToThread(BrowserThread::IO);
 }
 
 base::Callback<ChromeURLDataManagerBackend*(void)>
 ProfileImplIOData::Handle::GetChromeURLDataManagerBackendGetter() const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   LazyInitialize();
   return base::Bind(&ProfileIOData::GetChromeURLDataManagerBackend,
                     base::Unretained(io_data_));
 }
 
@@ skipping 391 matching lines @@
 void ProfileImplIOData::ClearNetworkingHistorySinceOnIOThread(
     base::Time time) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   LazyInitialize();
 
   DCHECK(transport_security_state());
   transport_security_state()->DeleteSince(time);
   DCHECK(http_server_properties_manager());
   http_server_properties_manager()->Clear();
 }