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diff --git a/Tools/Scripts/webkitpy/common/memoized.py b/Tools/Scripts/webkitpy/common/memoized.py
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+++ b/Tools/Scripts/webkitpy/common/memoized.py
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+# Copyright (c) 2010 Google Inc. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# Python does not (yet) seem to provide automatic memoization.  So we've
+# written a small decorator to do so.
+
+import functools
+
+
+class memoized(object):
+    def __init__(self, function):
+        self._function = function
+        self._results_cache = {}
+
+    def __call__(self, *args):
+        try:
+            return self._results_cache[args]
+        except KeyError:
+            # If we didn't find the args in our cache, call and save the results.
+            result = self._function(*args)
+            self._results_cache[args] = result
+            return result
+        # FIXME: We may need to handle TypeError here in the case
+        # that "args" is not a valid dictionary key.
+
+    # Use python "descriptor" protocol __get__ to appear
+    # invisible during property access.
+    def __get__(self, instance, owner):
+        # Return a function partial with obj already bound as self.
+        return functools.partial(self.__call__, instance)