Mike's change.

chrome/installer/gcapi/gcapi_omaha_experiment.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/installer/gcapi/gcapi_omaha_experiment.h"
 
 #include "base/string16.h"
 #include "base/stringprintf.h"
 #include "base/string_number_conversions.h"
 #include "base/time.h"
 #include "base/win/registry.h"
 #include "chrome/installer/util/browser_distribution.h"
 #include "chrome/installer/util/google_update_constants.h"
+#include "chrome/installer/gcapi/gcapi.h"
 
 using base::Time;
 using base::TimeDelta;
 using base::win::RegKey;
 
 namespace {
 
 const wchar_t kExperimentLabels[] = L"experiment_labels";
 
 const wchar_t* kExperimentAppGuids[] = {
@@ skipping 42 matching lines @@
 // Returns the number of weeks since 2/3/2003.
 int GetCurrentRlzWeek() {
   Time::Exploded february_third_2003_exploded = {2003, 2, 1, 3, 0, 0, 0, 0};
   Time f = Time::FromUTCExploded(february_third_2003_exploded);
   TimeDelta delta = Time::Now() - f;
   return delta.InDays() / 7;
 }
 
 }  // namespace
 
-bool SetOmahaExperimentLabel(const wchar_t* brand_code) {
+bool SetOmahaExperimentLabel(const wchar_t* brand_code, int shell_mode) {
   if (!brand_code) {
     return false;
   }
 
+  // When this function is invoked in standard, non-elevated shell, we default
+  // to writing the experiment label to HKCU.  When it is invoked in a UAC-
+  // elevated shell, we write the experiment label to HKLM.
+  HKEY registry_hive =
+      shell_mode == GCAPI_INVOKED_UAC_ELEVATION ? HKEY_LOCAL_MACHINE :
+                                                  HKEY_CURRENT_USER;
+
   int week_number = GetCurrentRlzWeek();
   if (week_number < 0 || week_number > 999)
     week_number = 999;
 
   string16 experiment_label;
   base::SStringPrintf(&experiment_label,
-                      L"%ls_%d|%ls",
+                      L"reacbrand=%ls_%d|%ls",
                       brand_code,
                       week_number,
                       BuildOmahaExperimentDateString().c_str());
 
   int successful_writes = 0;
   for (int i = 0; i < arraysize(kExperimentAppGuids); ++i) {
     string16 experiment_path(google_update::kRegPathClientState);
     experiment_path += L"\\";
     experiment_path += kExperimentAppGuids[i];
 
-    RegKey client_state(HKEY_LOCAL_MACHINE, experiment_path.c_str(),
+    RegKey client_state(registry_hive, experiment_path.c_str(),
                         KEY_SET_VALUE);
     if (client_state.Valid()) {
       if (client_state.WriteValue(kExperimentLabels,
                                   experiment_label.c_str()) == ERROR_SUCCESS) {
         successful_writes++;
       }
     }
   }
 
   return (successful_writes == arraysize(kExperimentAppGuids));
 }