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

chrome/browser/extensions/app_host/app_host_main.cc

Index: chrome/browser/extensions/app_host/app_host_main.cc
diff --git a/chrome/browser/extensions/app_host/app_host_main.cc b/chrome/browser/extensions/app_host/app_host_main.cc
index 10d044a57cbf93c2e524ceead7b669a8763e726d..30089a7c32ba7d51d19d46ed1cd2fb6d5dc5327a 100644
--- a/chrome/browser/extensions/app_host/app_host_main.cc
+++ b/chrome/browser/extensions/app_host/app_host_main.cc
@@ -7,16 +7,21 @@
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/process_util.h"
+#include "base/string16.h"

[erikwright (departed), 2012/09/13 01:13:44]

do you still need this?

[huangs, 2012/09/13 04:40:47]

Nope.  Deleted.

+#include "base/version.h"
+#include "chrome/browser/extensions/app_host/app_host_upgrade.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[] */) {
+  using namespace app_host;
+  using namespace chrome_launcher_support;
   base::AtExitManager exit_manager;
 
   // Initialize the commandline singleton from the environment.
   CommandLine::Init(0, NULL);
 
-  FilePath chrome_exe(chrome_launcher_support::GetAnyChromePath());
+  FilePath chrome_exe(GetAnyChromePath());
 
   if (chrome_exe.empty()) {
     LOG(INFO) << "No Chrome executable could be found. Let's install it.";
@@ -25,7 +30,7 @@ int main(int /* argc */, char* /* argv[] */) {
       LOG(ERROR) << "Failed to install the Chrome Binaries. Error: " << hr;
       return 1;
     } else {
-      chrome_exe = chrome_launcher_support::GetAnyChromePath();
+      chrome_exe = GetAnyChromePath();
       if (chrome_exe.empty()) {
         LOG(ERROR) << "Failed to find the Chrome Binaries despite a "
                    << "'successful' installation.";
@@ -38,13 +43,39 @@ int main(int /* argc */, char* /* argv[] */) {
   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;
   }
+
+  // If system-level Chrome Binary is installed, and if its version is
+  // newer than App Host's, then upgrade App Host by calling setup.exe.
+  Version chrome_binaries_version;
+  if (GetAppVersionForInstallationLevel(kMultiInstallAppGuid,
+                                        true,  // System-level.
+                                        &chrome_binaries_version)) {
+    Version app_host_version;
+    if (GetAppVersionForInstallationLevel(kChromeAppHostAppGuid,
+                                          false,  // User-level.
+                                          &app_host_version)) {
+      LOG(INFO) << "App Host version:        " << app_host_version.GetString();

[erikwright (departed), 2012/09/13 01:13:44]

Remove these two log statements, though it would be helpful to include the
versions in the statement at line 70.

[huangs, 2012/09/13 04:40:47]

Done.

+      LOG(INFO) << "Chrome binaries version: " <<
+          chrome_binaries_version.GetString();
+      if (app_host_version.IsOlderThan(chrome_binaries_version.GetString())) {
+        LOG(INFO) << "App Host out of date -- running setup.exe to upgrade";
+        if (!UpgradeAppHost(true)) {  // Use system-level setup.exe

[erikwright (departed), 2012/09/13 01:13:44]

No need for UpgradeAppHost to take a parameter. It should always be
system-level.

[huangs, 2012/09/13 04:40:47]

I did this to make the routine generic and dumb, so that the decision to choose
system-level is made by the caller.  The the comments on "why is this
system-level only" would be centralized.  Please reconsider.

+          LOG(ERROR) << "Failed to upgrade App Host";
+        }
+      }
+    } else {
+      LOG(INFO) << "Failed to get App Host version";
+    }
+  }  // Else there is no system-level Chrome, so do nothing.
+
+  return launch_result ? 0 : 1;
 }