Duplicate setup.exe into an identical executable and point Active Setup to that executable instead.

chrome/installer/util/util_constants.cc

Index: chrome/installer/util/util_constants.cc
diff --git a/chrome/installer/util/util_constants.cc b/chrome/installer/util/util_constants.cc
index 47c3605929bde05ce1befcf943da555c28163002..ef81206b493635480e2e9653907ce13f382cc4fa 100644
--- a/chrome/installer/util/util_constants.cc
+++ b/chrome/installer/util/util_constants.cc
@@ -193,6 +193,19 @@ const char kToastResultsKey[] = "toast-results-key";
 
 }  // namespace switches
 
+// The Active Setup executable will be an identical copy of setup.exe; this is
+// necessary because Windows' installer detection heuristics (which include
+// things like process name being "setup.exe") will otherwise force elevation
+// for non-admin users when setup.exe is launched. This is mitigated by adding
+// requestedExecutionLevel="asInvoker" to setup.exe's manifest on Vista+, but
+// there is no such manifest entry on Windows XP (which results in
+// crbug.com/166473). The name "as.exe" is short and obscur on purpose so that:
+// 1) It is not detected as an installer by any naming-based heuristic.
+// 2) No adventurous user feels like running this will solve his problems (as
+//    something like "user_config.exe" could otherwise suggest).
+// TODO(gab): Rename setup.exe itself altogether and use the same binary for
+// Active Setup.
+const wchar_t kActiveSetupExe[] = L"as.exe";

[grt (UTC plus 2), 2013/01/09 14:13:15]

This name is too short and obscure. How about using whatever name you'd like
setup.exe to have? chromesu.exe (8.3!)?

[gab, 2013/01/09 15:39:42]

sgtm :)!

 const wchar_t kChromeAppHostExe[] = L"app_host.exe";
 const wchar_t kChromeDll[] = L"chrome.dll";
 const wchar_t kChromeExe[] = L"chrome.exe";