Remove _unit_test_config hack, instead use FileSystem() in cpp.py & cpp_unittest.py

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

Index: Tools/Scripts/webkitpy/common/system/filesystem.py
diff --git a/Tools/Scripts/webkitpy/common/system/filesystem.py b/Tools/Scripts/webkitpy/common/system/filesystem.py
index 3786c6fed2222e6043fca5b316192878de2fe7d4..4ad3b1cfd37802a751f2ca724b14a0f8efc9f890 100644
--- a/Tools/Scripts/webkitpy/common/system/filesystem.py
+++ b/Tools/Scripts/webkitpy/common/system/filesystem.py
@@ -206,11 +206,11 @@ class FileSystem(object):
     def open_text_file_for_writing(self, path):
         return codecs.open(path, 'w', 'utf8')
 
-    def read_text_file(self, path):
+    def read_text_file(self, path, errors='strict'):

[Dirk Pranke, 2013/10/22 19:17:03]

Are you sure we need this? I.e., does test-webkitpy include test cases that need
replaced content?

         """Return the contents of the file at the given path as a Unicode string.
 
         The file is read assuming it is a UTF-8 encoded file with no BOM."""
-        with codecs.open(path, 'r', 'utf8') as f:
+        with codecs.open(path, 'r', 'utf8', errors) as f:
             return f.read()
 
     def write_text_file(self, path, contents):