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

chrome/tools/launcher_support/chrome_launcher_support.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/tools/launcher_support/chrome_launcher_support.h"
+
+#include <windows.h>
+#include <tchar.h>
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/path_service.h"
+#include "base/string16.h"
+#include "base/win/registry.h"
+
+namespace {
+
+// TODO(erikwright): These constants are duplicated all over the place.
+// Consolidate them somehow.

[robertshield, 2012/06/13 18:01:53]

There are similarly worded TODO(robertshield)s elsewhere in the code base.
Welcome to the club :-)

[Vitaly Buka (NO REVIEWS), 2012/06/13 18:08:19]

Please keep in mind that we'd like to avoid depend on large Chrome targets.
On 2012/06/13 18:01:53, robertshield wrote:

[erikwright (departed), 2012/06/13 19:43:43]

Absolutely. My client of this library is under a similar constraint.

+const wchar_t kChromeRegClientStateKey[] =
+    L"Software\\Google\\Update\\ClientState\\"
+    L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
+
+const wchar_t kGoogleChromeExePath[] =
+    L"Google\\Chrome\\Application\\chrome.exe";
+
+const wchar_t kUninstallStringField[] = L"UninstallString";
+
+const wchar_t kChromeExe[] = L"chrome.exe";
+
+}  // namespace
+
+namespace chrome_launcher_support {
+
+FilePath GetAnyChromePath() {
+  FilePath chrome_path = GetChromePathForInstallationLevel(

[grt (UTC plus 2), 2012/06/13 18:00:10]

i've been told repeatedly that chromium prefers FilePath chrome_path(...) as per
gotw#1.

[erikwright (departed), 2012/06/13 19:43:43]

Done.

+      SYSTEM_LEVEL_INSTALLATION);
+  if (!chrome_path.empty())
+    return chrome_path;
+  chrome_path = GetChromePathForInstallationLevel(USER_LEVEL_INSTALLATION);
+  if (!chrome_path.empty())
+    return chrome_path;
+  if (PathService::Get(base::DIR_PROGRAM_FILES, &chrome_path)) {
+    chrome_path.Append(kGoogleChromeExePath);

[grt (UTC plus 2), 2012/06/13 18:00:10]

chrome_path = chrome_path.Append(kGoogleChromeExePath);

[erikwright (departed), 2012/06/13 19:43:43]

Ouch! Perhaps that's a sign that I can just remove this case, since this is
actually just moved from Cloud Print.

Done.

[Vitaly Buka (NO REVIEWS), 2012/06/13 20:18:37]

Yep. My mistake. But I still believe it might be useful.

On 2012/06/13 19:43:43, erikwright wrote:

+    if (file_util::PathExists(chrome_path))
+      return chrome_path;
+  }
+  return FilePath();
+}
+
+FilePath GetChromePathForInstallationLevel(InstallationLevel level) {

[grt (UTC plus 2), 2012/06/13 18:00:10]

will this ever be used by code that wishes to find a canary install?  if so,
canary is user-level only and has a different guid.

[erikwright (departed), 2012/06/13 19:43:43]

I would say probably not. But I'm not sure how to enforce it or document it in a
way that would catch such a mistake if it were made :(

+  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