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

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.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/renderer_host/chrome_resource_dispatcher_host_delegate.h"
 
 #include "base/logging.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/download/download_request_limiter.h"
 #include "chrome/browser/download/download_resource_throttle.h"
 #include "chrome/browser/download/download_util.h"
 #include "chrome/browser/extensions/user_script_listener.h"
 #include "chrome/browser/external_protocol/external_protocol_handler.h"
+#include "chrome/browser/google/google_util.h"
 #include "chrome/browser/instant/instant_loader.h"
 #include "chrome/browser/net/load_timing_observer.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_manager_factory.h"
 #include "chrome/browser/prerender/prerender_tracker.h"
 #include "chrome/browser/profiles/profile_io_data.h"
 #include "chrome/browser/renderer_host/chrome_url_request_user_data.h"
 #include "chrome/browser/renderer_host/safe_browsing_resource_throttle.h"
 #include "chrome/browser/renderer_host/transfer_navigation_resource_throttle.h"
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
@@ skipping 131 matching lines @@
     throttles->push_back(new TransferNavigationResourceThrottle(request));
 
 #if defined(OS_CHROMEOS)
     // We check offline first, then check safe browsing so that we still can
     // block unsafe site after we remove offline page.
     throttles->push_back(new OfflineResourceThrottle(
         child_id, route_id, request, resource_context));
 #endif
   }
 
+  AppendChromeMetricsHeaders(request, resource_context, resource_type);
+
   AppendStandardResourceThrottles(request,
                                   resource_context,
                                   child_id,
                                   route_id,
                                   resource_type,
                                   throttles);
 }
 
 void ChromeResourceDispatcherHostDelegate::DownloadStarting(
     net::URLRequest* request,
@@ skipping 110 matching lines @@
   }
 #endif
 
   content::ResourceThrottle* throttle =
       user_script_listener_->CreateResourceThrottle(request->url(),
                                                     resource_type);
   if (throttle)
     throttles->push_back(throttle);
 }
 
+void ChromeResourceDispatcherHostDelegate::AppendChromeMetricsHeaders(
+    net::URLRequest* request,
+    content::ResourceContext* resource_context,
+    ResourceType::Type resource_type) {
+  // Note our criteria for attaching Chrome experiment headers:
+  // 1. We only transmit to *.google.<TLD> domains. NOTE that this use of
+  //    google_util helpers to check this does not guarantee that the URL is
+  //    Google-owned, only that it is of the form *.google.<TLD>. In the future
+  //    we may choose to reinforce this check.
+  // 2. We only transmit for non-Incognito profiles.
+  // 3. For the X-Chrome-UMA-Enabled bit, we only set it if UMA is in fact
+  //    enabled for this install of Chrome.
+  ProfileIOData* io_data = ProfileIOData::FromResourceContext(resource_context);
+  if (google_util::IsGoogleDomainUrl(request->url().spec(),
+                                     google_util::ALLOW_SUBDOMAIN) &&
+      !io_data->is_incognito() && io_data->enable_metrics()->GetValue()) {
+    request->SetExtraRequestHeaderByName("X-Chrome-UMA-Enabled",
+                                         "1",
+                                         false);
+  }
+}
+
 bool ChromeResourceDispatcherHostDelegate::ShouldForceDownloadResource(
     const GURL& url, const std::string& mime_type) {
   // Special-case user scripts to get downloaded instead of viewed.
   return UserScript::IsURLUserScript(url, mime_type);
 }
 
 void ChromeResourceDispatcherHostDelegate::OnResponseStarted(
     net::URLRequest* request,
     content::ResourceResponse* response,
     IPC::Message::Sender* sender) {
@@ skipping 31 matching lines @@
 #if defined(ENABLE_ONE_CLICK_SIGNIN)
   const ResourceRequestInfo* info = ResourceRequestInfo::ForRequest(request);
 
   // See if the response contains the Google-Accounts-SignIn header.  If so,
   // then the user has just finished signing in, and the server is allowing the
   // browser to suggest connecting the user's profile to the account.
   OneClickSigninHelper::ShowInfoBarIfPossible(request, info->GetChildID(),
                                               info->GetRouteID());
 #endif
 }