[cros] RLZ tracking can be turned off via a flag file.

chrome/browser/google/google_util_chromeos.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 "base/basictypes.h"
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/string_util.h"
@@ skipping 22 matching lines @@
   TrimWhitespace(brand, TRIM_ALL, &brand);
   return brand;
 }
 
 // Sets the brand code to |brand|.
 void SetBrand(const base::Closure& callback, const std::string& brand) {
   g_browser_process->local_state()->SetString(prefs::kRLZBrand, brand);
   callback.Run();
 }
 
+// True if brand code has been cleared for the current session.
+bool g_brand_empty = false;
+
 }  // namespace
 
+void ClearBrandForCurrentSession() {
+  DCHECK(
+      !content::BrowserThread::IsWellKnownThread(content::BrowserThread::UI) ||
+      content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  g_brand_empty = true;
+}
+
 std::string GetBrand() {
   DCHECK(
       !content::BrowserThread::IsWellKnownThread(content::BrowserThread::UI) ||
       content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  if (g_brand_empty)
+    return std::string();
   DCHECK(g_browser_process->local_state());
   return g_browser_process->local_state()->GetString(prefs::kRLZBrand);
 }
 
 void SetBrandFromFile(const base::Closure& callback) {
   base::PostTaskAndReplyWithResult(
       base::WorkerPool::GetTaskRunner(false /* task_is_slow */),
       FROM_HERE,
       base::Bind(&ReadBrandFromFile),
       base::Bind(&SetBrand, callback));
 }
 
 }  // namespace chromeos
 }  // namespace google_util