Remove a bunch of unused webkitpy code from tool/, common/checkout/ and common/config/

Tools/Scripts/webkitpy/tool/steps/abstractstep.py

Index: Tools/Scripts/webkitpy/tool/steps/abstractstep.py
diff --git a/Tools/Scripts/webkitpy/tool/steps/abstractstep.py b/Tools/Scripts/webkitpy/tool/steps/abstractstep.py
index ff8a752b8893773942286a4059126759eec0c8cd..9d7f2e07373665502137a8f32dd15e4effba2228 100644
--- a/Tools/Scripts/webkitpy/tool/steps/abstractstep.py
+++ b/Tools/Scripts/webkitpy/tool/steps/abstractstep.py
@@ -40,33 +40,6 @@ class AbstractStep(object):
     def _exit(self, code):
         sys.exit(code)
 
-    def _changed_files(self, state):
-        return self.cached_lookup(state, "changed_files")
-
-    _well_known_keys = {
-        # FIXME: Should this use state.get('bug_id') or state.get('patch').bug_id() like UpdateChangeLogsWithReviewer does?
-        "bug": lambda self, state: self._tool.bugs.fetch_bug(state["bug_id"]),
-        # bug_title can either be a new title given by the user, or one from an existing bug.
-        "bug_title": lambda self, state: self.cached_lookup(state, 'bug').title(),
-        "changed_files": lambda self, state: self._tool.scm().changed_files(self._options.git_commit),
-        "diff": lambda self, state: self._tool.scm().create_patch(self._options.git_commit, changed_files=self._changed_files(state)),
-        # Absolute path to ChangeLog files.
-        "changelogs": lambda self, state: self._tool.checkout().modified_changelogs(self._options.git_commit, changed_files=self._changed_files(state)),
-    }
-
-    def cached_lookup(self, state, key, promise=None):
-        if state.get(key):
-            return state[key]
-        if not promise:
-            promise = self._well_known_keys.get(key)
-        state[key] = promise(self, state)
-        return state[key]
-
-    def did_modify_checkout(self, state):
-        state["diff"] = None
-        state["changelogs"] = None
-        state["changed_files"] = None
-
     @classmethod
     def options(cls):
         return [