Fix runtime error in copytree() MockFileSystem

Tools/Scripts/webkitpy/common/system/filesystem_mock.py

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@@ skipping 373 matching lines @@
             # cases like path='/foo/b' and f='/foo/bar/baz'.
             if f == path or f.startswith(path + self.sep):
                 self.files[f] = None
 
         self.dirs = set(filter(lambda d: not (d == path or d.startswith(path + self.sep)), self.dirs))
 
     def copytree(self, source, destination):
         source = self.normpath(source)
         destination = self.normpath(destination)
 
-        for source_file in self.files:
+        for source_file in self.files.keys():

[Dirk Pranke, 2014/08/27 23:42:45]

this change is fine for Python 2.7, but I think it will have the same problem in
python 3 that the 'for ... in dict' old version does, so it might be better to 
change this to "for source_file in list(self.files)", which is safe in Python 3.

Not that we actually support Python 3 yet, of course ...

[patro, 2014/09/01 09:14:02]

Done.

             if source_file.startswith(source):
                 destination_path = self.join(destination, self.relpath(source_file, source))
                 self.maybe_make_directory(self.dirname(destination_path))
                 self.files[destination_path] = self.files[source_file]
 
     def split(self, path):
         idx = path.rfind(self.sep)
         if idx == -1:
             return ('', path)
         return (path[:idx], path[(idx + 1):])
@@ skipping 71 matching lines @@
         return self.data.readline(length)
 
     def __iter__(self):
         return self.data.__iter__()
 
     def next(self):
         return self.data.next()
 
     def seek(self, offset, whence=os.SEEK_SET):
         self.data.seek(offset, whence)