GCAPI should append to the existing experiment_labels instead of clobbering them.

chrome/installer/gcapi/gcapi_test_registry_overrider.cc

Index: chrome/installer/gcapi/gcapi_test_registry_overrider.cc
diff --git a/chrome/installer/gcapi/gcapi_test_registry_overrider.cc b/chrome/installer/gcapi/gcapi_test_registry_overrider.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fe90cdffd305f797dfb202247f0a8464dd40b8b3
--- /dev/null
+++ b/chrome/installer/gcapi/gcapi_test_registry_overrider.cc
@@ -0,0 +1,23 @@
+// Copyright 2013 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_test_registry_overrider.h"
+
+#include "base/guid.h"
+#include "base/strings/string16.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+
+GCAPITestRegistryOverrider::GCAPITestRegistryOverrider() {
+  // Override keys - this is undone during destruction.
+  string16 hkcu_override = base::StringPrintf(
+      L"hkcu_override\\%ls", ASCIIToWide(base::GenerateGUID()));
+  override_manager_.OverrideRegistry(HKEY_CURRENT_USER, hkcu_override);
+  string16 hklm_override = base::StringPrintf(
+      L"hklm_override\\%ls", ASCIIToWide(base::GenerateGUID()));
+  override_manager_.OverrideRegistry(HKEY_LOCAL_MACHINE, hklm_override);
+}
+
+GCAPITestRegistryOverrider::~GCAPITestRegistryOverrider() {
+}