Give SxS distribution its own registration GUIDs.

chrome/installer/util/install_util.cc

Index: chrome/installer/util/install_util.cc
diff --git a/chrome/installer/util/install_util.cc b/chrome/installer/util/install_util.cc
index c8c037df823364a081b3ebac240cb974244d3e27..f1eb705d3763c8ca5308e26eaea8e086000ed97d 100644
--- a/chrome/installer/util/install_util.cc
+++ b/chrome/installer/util/install_util.cc
@@ -365,10 +365,31 @@ bool CheckIsChromeSxSProcess() {
   PathService::Get(base::DIR_EXE, &exe_dir);
   string16 chrome_sxs_dir(installer::kGoogleChromeInstallSubDir2);
   chrome_sxs_dir.append(installer::kSxSSuffix);
-  return base::FilePath::CompareEqualIgnoreCase(
-          exe_dir.BaseName().value(), installer::kInstallBinaryDir) &&
-      base::FilePath::CompareEqualIgnoreCase(
-          exe_dir.DirName().BaseName().value(), chrome_sxs_dir);
+
+  // This is SxS if current EXE is in or under (possibly multiple levels under)
+  // |chrome_sxs_dir|\|installer::kInstallBinaryDir|
+  std::vector<base::FilePath::StringType> components;
+  exe_dir.GetComponents(&components);
+  auto iter = components.begin();
+  while (iter != components.end()) {

[gab, 2013/09/06 18:40:08]

I would say it's faster (and perhaps slightly more reliable) to do a reverse
lookup (i.e. using reverse iterators); and look for kInstallBinaryDir and make
sure it's under chrome_sxs_dir.

[zturner, 2013/09/06 20:53:16]

Done.

+    if (!base::FilePath::CompareEqualIgnoreCase(*iter, chrome_sxs_dir)) {
+      ++iter;
+      continue;
+    }
+
+    if (++iter == components.end())
+      return false;
+
+    if (base::FilePath::CompareEqualIgnoreCase(*iter,
+        installer::kInstallBinaryDir))
+      return true;
+
+    // Don't increment the iterator here.  It's theoretically possible to have
+    // a path that looks like "Chrome SxS\Chrome SxS\Application" which should
+    // still be treated as a SxS installation.

[gab, 2013/09/06 18:40:08]

This case is safer with the reverse iteration proposed above.

[zturner, 2013/09/06 20:53:16]

Done.

+  }
+
+  return false;
 }
 
 bool InstallUtil::IsChromeSxSProcess() {