Fix base::CopyDirectory() and JumpListIcons(Old) folders' operation logic

base/files/file_util_win.cc

Index: base/files/file_util_win.cc
diff --git a/base/files/file_util_win.cc b/base/files/file_util_win.cc
index d70454df3836a7067f71eecf5a0ae8673376f474..629658447d848b53630c2638d4ae478990ba498b 100644
--- a/base/files/file_util_win.cc
+++ b/base/files/file_util_win.cc
@@ -177,9 +177,10 @@ bool CopyDirectory(const FilePath& from_path, const FilePath& to_path,
   FilePath real_from_path = MakeAbsoluteFilePath(from_path);
   if (real_from_path.empty())
     return false;
+  // Note: it's important to use IsParent() here as string comparison would

[grt (UTC plus 2), 2016/12/15 09:23:55]

nit: i think this comment is unnecessary. the FilePath API should be used
because it's the right thing. otherwise, why is this one use of IsParent so
important that this comment is justified in comparison to every other use of
IsParent in the codebase?

+  // result in a false negative, e.g. on C:\bar\Foo versus C:\bar\FooOld.
   if (real_to_path.value().size() >= real_from_path.value().size() &&

[grt (UTC plus 2), 2016/12/15 09:23:55]

this "optimization" seems wrong to me -- either a FilePath is treated like a
string (as was with the old code), or it's treated as a FilePath (as it is with
the call to IsParent). i think it's a mistake to mix the two like this.

-      real_to_path.value().compare(0, real_from_path.value().size(),
-                                   real_from_path.value()) == 0) {
+      real_from_path.IsParent(real_to_path)) {

[grt (UTC plus 2), 2016/12/15 09:23:55]

please make this same fix in file_util_posix

     return false;
   }