If Chrome Binaries version > App Host version, then update App Host.

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
index c92f771a4735c3a0a141056e05840e2c98d9633a..5cb0cb37c27d1024359e058a17e8c44da32a9cc3 100644
--- a/chrome/installer/launcher_support/chrome_launcher_support.cc
+++ b/chrome/installer/launcher_support/chrome_launcher_support.cc
@@ -8,6 +8,7 @@
 #include <tchar.h>
 #include "base/file_path.h"
 #include "base/file_util.h"
+#include "base/logging.h"
 #ifndef OFFICIAL_BUILD
 #include "base/path_service.h"
 #endif
@@ -16,14 +17,15 @@
 
 namespace {
 
-// TODO(erikwright): These constants are duplicated all over the place.
-// Consolidate them somehow.
-const wchar_t kChromeRegClientStateKey[] =
+// TODO(huangs) Refactor the constants:
+// http://code.google.com/p/chromium/issues/detail?id=148538

[grt (UTC plus 2), 2012/09/13 20:04:12]

same comment about shrinking this

[huangs, 2012/09/13 22:25:37]

Done.

[grt (UTC plus 2), 2012/09/14 14:26:52]

Same comment about putting bug number on same line as comment.

+const wchar_t kChromeBinariesRegClientStateKey[] =
     L"Software\\Google\\Update\\ClientState\\"
-    L"{8A69D345-D564-463c-AFF1-A69D9E530F96}";
+    L"{4DC8B4CA-1BDA-483e-B5FA-D3C12E15B62D}";
 
 const wchar_t kUninstallStringField[] = L"UninstallString";
 
+// Copied from util_constants.cc.
 const wchar_t kChromeExe[] = L"chrome.exe";
 
 #ifndef OFFICIAL_BUILD
@@ -56,38 +58,41 @@ FilePath GetAnyChromePath() {
   return chrome_path;
 }
 
-FilePath GetChromePathForInstallationLevel(InstallationLevel level) {
+FilePath GetSetupExeForInstallationLevel(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.
+  RegKey reg_key;
+  if (reg_key.Open(root_key, kChromeBinariesRegClientStateKey,

[erikwright (departed), 2012/09/13 19:27:49]

If we can't find the ChromeBinaries, next try Chrome.

[huangs, 2012/09/13 22:25:37]

Sorry for the no-op; misread comments!
Done.  Extracted common code to GetSetupExeFromRegistry().  Also, prioritizing
code symmetry over slight efficiency (e.g. not initializing setup_exe_path by
constructor).

+                   KEY_QUERY_VALUE) == ERROR_SUCCESS) {
     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);
-      }
+      FilePath setup_exe_path(uninstall);
+      if (file_util::PathExists(setup_exe_path))
+        return setup_exe_path;
     }
   }
+  return FilePath();
+}
 
-  if (file_util::PathExists(chrome_exe_path))
-    return chrome_exe_path;
-
+FilePath GetChromePathForInstallationLevel(InstallationLevel level) {
+  FilePath setup_exe_path(GetSetupExeForInstallationLevel(level));
+  if (!setup_exe_path.empty()) {
+    FilePath chrome_exe_path;
+    // 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.
+    chrome_exe_path =
+        setup_exe_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 = chrome_exe_path.DirName().DirName().Append(kChromeExe);
+    }
+    if (file_util::PathExists(chrome_exe_path))
+      return chrome_exe_path;
+  }
   return FilePath();
 }