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..70678af80e91671ecfc999806a0e25e1b65ecef7 100644
--- a/chrome/installer/util/install_util.cc
+++ b/chrome/installer/util/install_util.cc
@@ -365,10 +365,28 @@ 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|
+  typedef std::vector<base::FilePath::StringType> ComponentsType;

[gab, 2013/09/10 19:08:57]

I don't feel this typedef is necessary; it adds complexity only to maybe save a
single line wrap below (and it requires a line of itself to declare...).

[zturner, 2013/09/11 20:19:53]

Well, it's just that 

std::vector<base::FilePath::StringType>::const_reverse_iterator

is almost an entire line just by itself, and it has to be used in at least two
places.  Seems like using the typedef is in the same spirit of the Google Style
Guide's recommendation to use auto when long type names are involved, but in a
way that doesn't require C++11.

[grt (UTC plus 2), 2013/09/11 20:41:52]

I like the typedef, although I don't like "Type" in the name of types. I'd like
it better if it was Strings or StringVector, since the "components" are strings.
FWIW, this has been discussed on chromium-dev:
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/qSrl_UAqAkQ/dis....

[gab, 2013/09/11 20:53:49]

Well, one of the 2 places is the line just below this one where it will fit (I
think).

Actually, looking at this some more, I agree that the ifdef could be nice for
the iterator and used as such:

  typedef std::vector<base::FilePath::StringType>::const_reverse_iterator 
          ComponentsIterator;

  if (components.size() < 2)
    return false;

  for (ComponentsIterator current = components.rbegin(), 
           ComponentsIterator parent = current + 1;
       parent != components.rend(); current = parent++) {
    ...
  }

+  ComponentsType components;
+  exe_dir.GetComponents(&components);
+  ComponentsType::const_reverse_iterator iter = components.rbegin();
+  while (iter != components.rend()) {
+    auto next = iter+1;

[gab, 2013/09/10 19:08:57]

I still think you can't use "auto" in Chromium (ref C++11 discussion linked to
in earlier CR).

I would name this variable something like "parent" instead and use a const&
instead.

i.e.
const base::FilePath::StringType& parent = *(iter + 1);

[zturner, 2013/09/11 20:19:53]

You're right, I just missed this one.
Won't work exactly like that because I need to check iter+1 against rend()
before I can de-reference it, so the best way is to make another iterator on the
stack and increment it similar to how I was doing with the auto.  That was the
main reason for using the typedef.

+
+    if (base::FilePath::CompareEqualIgnoreCase(*iter,
+        installer::kInstallBinaryDir)) {
+
+      if (next != components.rend() &&

[gab, 2013/09/10 19:08:57]

Use "&&" to continue previous condition instead of having an if inside an if.

+          (base::FilePath::CompareEqualIgnoreCase(*next, chrome_sxs_dir)))
+        return true;
+    }
+
+    iter = next;

[gab, 2013/09/10 19:08:57]

Feels like a for loop to me;

e.g.,:

for (ComponentsType::const_reverse_iterator iter = components.rbegin(); 
      iter != components.rend(); ++iter) {
...
}

[zturner, 2013/09/11 20:19:53]

Yea, but then if I don't use the typedef it looks pretty unpleasant, at least to
me.  

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