Factor out logic to find chrome.exe from Omaha client state.

chrome/installer/launcher_support/chrome_launcher_support.cc

Index: chrome/installer/launcher_support/chrome_launcher_support.cc
diff --git a/chrome/installer/launcher_support/chrome_launcher_support.cc b/chrome/installer/launcher_support/chrome_launcher_support.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c92f771a4735c3a0a141056e05840e2c98d9633a
--- /dev/null
+++ b/chrome/installer/launcher_support/chrome_launcher_support.cc
@@ -0,0 +1,94 @@
+// 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/launcher_support/chrome_launcher_support.h"
+
+#include <windows.h>
+#include <tchar.h>
+#include "base/file_path.h"
+#include "base/file_util.h"
+#ifndef OFFICIAL_BUILD
+#include "base/path_service.h"
+#endif
+#include "base/string16.h"
+#include "base/win/registry.h"
+
+namespace {
+
+// TODO(erikwright): These constants are duplicated all over the place.
+// Consolidate them somehow.
+const wchar_t kChromeRegClientStateKey[] =
+    L"Software\\Google\\Update\\ClientState\\"
+    L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
+
+const wchar_t kUninstallStringField[] = L"UninstallString";
+
+const wchar_t kChromeExe[] = L"chrome.exe";
+
+#ifndef OFFICIAL_BUILD
+FilePath GetDevelopmentChrome() {
+  FilePath current_directory;
+  if (PathService::Get(base::DIR_EXE, &current_directory)) {
+    FilePath chrome_exe_path(current_directory.Append(kChromeExe));
+    if (file_util::PathExists(chrome_exe_path))
+      return chrome_exe_path;
+  }
+  return FilePath();
+}
+#endif
+
+}  // namespace
+
+namespace chrome_launcher_support {
+
+FilePath GetAnyChromePath() {
+  FilePath chrome_path;
+#ifndef OFFICIAL_BUILD
+  // For development mode, chrome.exe should be in same dir as the stub.
+  chrome_path = GetDevelopmentChrome();
+#endif
+  if (chrome_path.empty())
+    chrome_path = GetChromePathForInstallationLevel(SYSTEM_LEVEL_INSTALLATION);
+  if (chrome_path.empty())
+    chrome_path = GetChromePathForInstallationLevel(USER_LEVEL_INSTALLATION);
+
+  return chrome_path;
+}
+
+FilePath GetChromePathForInstallationLevel(InstallationLevel level) {
+  using base::win::RegKey;
+  HKEY root_key = (level == USER_LEVEL_INSTALLATION ?
+                   HKEY_CURRENT_USER :
+                   HKEY_LOCAL_MACHINE);
+  RegKey reg_key(root_key, kChromeRegClientStateKey, KEY_QUERY_VALUE);
+
+  FilePath chrome_exe_path;
+
+  if (reg_key.Valid()) {
+    // Now grab the uninstall string from the appropriate ClientState key
+    // and use that as the base for a path to chrome.exe.
+    string16 uninstall;
+    if (reg_key.ReadValue(kUninstallStringField, &uninstall) == ERROR_SUCCESS) {
+      // The uninstall path contains the path to setup.exe which is two levels
+      // down from chrome.exe. Move up two levels (plus one to drop the file
+      // name) and look for chrome.exe from there.
+      FilePath uninstall_path(uninstall);
+      chrome_exe_path =
+          uninstall_path.DirName().DirName().DirName().Append(kChromeExe);
+      if (!file_util::PathExists(chrome_exe_path)) {
+        // By way of mild future proofing, look up one to see if there's a
+        // chrome.exe in the version directory
+        chrome_exe_path =
+            uninstall_path.DirName().DirName().Append(kChromeExe);
+      }
+    }
+  }
+
+  if (file_util::PathExists(chrome_exe_path))
+    return chrome_exe_path;
+
+  return FilePath();
+}
+
+}  // namespace chrome_launcher_support