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..8c1da3add5329282ec1b28dbe878fd1487331c02 100644
--- a/chrome/installer/util/install_util.cc
+++ b/chrome/installer/util/install_util.cc
@@ -365,10 +365,26 @@ 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);
+  // We need at least 1 element in the array for the behavior of the following
+  // loop to be defined.  This should always be true, since we're splitting the
+  // path to our executable.

[grt (UTC plus 2), 2013/09/12 14:04:53]

this is splitting the dir containing the executable. would this not be empty if
the executable happened to be at the root of a volume? we don't install chrome
that way, but it would be a shame for chrome to crash if it were run like that.

[gab, 2013/09/13 02:02:36]

zturner:
I would say then that it's clearer to mention that, the current comment is
unclear imo; i.e., I'd replace:

"since we're splitting the path to our executable."
with
"since the path will at least contain a component for the drive letter."

+  DCHECK(!components.empty());
+  typedef std::vector<base::FilePath::StringType>::const_reverse_iterator
+      ComponentsIterator;
+  for (ComponentsIterator current = components.rbegin(), parent = current + 1;
+       parent != components.rend(); current = parent++) {
+    if (base::FilePath::CompareEqualIgnoreCase(
+            *current, installer::kInstallBinaryDir) &&
+        base::FilePath::CompareEqualIgnoreCase(*parent, chrome_sxs_dir))

[grt (UTC plus 2), 2013/09/12 14:04:53]

nit: use braces for multi-line conditional.

[gab, 2013/09/13 02:02:36]

ping on this.

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