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

chrome/browser/extensions/app_host/app_host_main.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 "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/process_util.h"
+#include "base/string16.h"
+#include "base/string_util.h"
+#include "base/version.h"
 #include "chrome/browser/extensions/app_host/binaries_installer.h"
 #include "chrome/installer/launcher_support/chrome_launcher_support.h"
 
 int main(int /* argc */, char* /* argv[] */) {
   base::AtExitManager exit_manager;
 
   // Initialize the commandline singleton from the environment.
   CommandLine::Init(0, NULL);
 
   FilePath chrome_exe(chrome_launcher_support::GetAnyChromePath());
@@ skipping 11 matching lines @@
                    << "'successful' installation.";
         return 1;
       }
     }
   }
 
   CommandLine chrome_exe_command_line(chrome_exe);
   chrome_exe_command_line.AppendArguments(
       *CommandLine::ForCurrentProcess(), false);
 
-  if (base::LaunchProcess(chrome_exe_command_line,
-                          base::LaunchOptions(),
-                          NULL)) {
+  // Launch Chrome before checking for updates, for faster user experience.
+  bool launch_result = base::LaunchProcess(chrome_exe_command_line,
+                                           base::LaunchOptions(),
+                                           NULL);
+  if (launch_result) {
     LOG(INFO) << "Delegated to Chrome executable at " << chrome_exe.value();
-    return 0;
   } else {
     LOG(INFO) << "Failed to launch Chrome executable at " << chrome_exe.value();
-    return 1;
   }
+
+  // Upgrade App Host if its version is less than CHrome Binary's.

[erikwright (departed), 2012/09/12 15:53:50]

CHrome -> Chrome

[huangs, 2012/09/12 19:24:27]

Done.

+  string16 app_host_version_str;
+  string16 chrome_binaries_version_str;
+  if (chrome_launcher_support::GetAppHostVersionString(&app_host_version_str) &&

[erikwright (departed), 2012/09/12 15:53:50]

It seems to me these methods should do the conversion to base::Version
themselves.

[huangs, 2012/09/12 19:24:27]

Done.

+      chrome_launcher_support::GetAnyChromeBinariesVersionString(

[erikwright (departed), 2012/09/12 15:53:50]

All of this only applies if ChromeBinaries are at system-level. So how about
GetSystemLevelChromeBinariesVersion() .

[huangs, 2012/09/12 19:24:27]

Done.

+          &chrome_binaries_version_str)) {
+    LOG(INFO) << "App Host version: " << app_host_version_str;
+    LOG(INFO) << "Chrome binaries version: " << chrome_binaries_version_str;
+    if (Version(WideToASCII(app_host_version_str)).IsOlderThan(
+        WideToASCII(chrome_binaries_version_str))) {
+      LOG(INFO) << "App Host out of date -- running setup.exe to upgrade";
+      if (!chrome_launcher_support::UpgradeAppHost()) {
+        LOG(INFO) << "Failed to upgrade App Host";
+      }
+    }
+  } else {
+    LOG(INFO) << "Failed to get the version for App Host or Chrome Binaries";
+  }
+
+  return launch_result ? 0 : 1;
 }