Refactor SetOmahaExperimentLabel out of gcpai and into install_util.

chrome/installer/gcapi/gcapi_dll.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 <windows.h>
+
+#include "base/at_exit.h"
+#include "base/command_line.h"
+#include "base/logging.h"
+
 // Visual Studio needs at least one C++ file in project http://goo.gl/roro9
+
+namespace {
+base::AtExitManager* g_exit_manager = NULL;
+}
+
+// DLL Entry Point - This is necessary to initialize basic things like the
+// CommandLine and Logging components needed by functions in the DLL.
+extern "C" BOOL WINAPI DllMain(HINSTANCE instance,
+                               DWORD reason,
+                               LPVOID reserved) {
+  if (reason == DLL_PROCESS_ATTACH) {
+    g_exit_manager = new base::AtExitManager();
+    CommandLine::Init(0, NULL);
+    logging::InitLogging(
+        NULL,
+        logging::LOG_ONLY_TO_SYSTEM_DEBUG_LOG,
+        logging::LOCK_LOG_FILE,
+        logging::DELETE_OLD_LOG_FILE,
+        logging::DISABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS);
+  } else if (reason == DLL_PROCESS_DETACH) {
+    CommandLine::Reset();
+    delete g_exit_manager;
+    g_exit_manager = NULL;
+  }
+
+  return TRUE;
+}