[varStore] remove unused _Encoding methods

Lib/fontTools/varLib/varStore.py

@@ -412,25 +412,6 @@ class _Encoding(object):
     def extend(self, lst):
         self.items.update(lst)
 
-    def get_room(self):
-        """Maximum number of bytes that can be added to characteristic
-        while still being beneficial to merge it into another one."""
-        count = len(self.items)
-        return max(0, (self.overhead - 1) // count - self.width)
-
-    room = property(get_room)
-
-    def get_gain(self):
-        """Maximum possible byte gain from merging this into another
-        characteristic."""
-        count = len(self.items)
-        return max(0, self.overhead - count)
-
-    gain = property(get_gain)
-
-    def gain_sort_key(self):
-        return self.gain, self.chars
-
     def width_sort_key(self):
         return self.width, self.chars
 
@@ -534,13 +515,9 @@ def VarStore_optimize(self, use_NO_VARIATION_INDEX=True, quantization=1):
     # of the old encoding is completely eliminated. However, each row
     # now would require more bytes to encode, to the tune of one byte
     # per characteristic bit that is active in the new encoding but not
-    # in the old one. The number of bits that can be added to an encoding
+    # in the old one.
-    # while still beneficial to merge it into another encoding is called
-    # the "room" for that encoding.
     #
-    # The "gain" of an encodings is the maximum number of bytes we can
+    # The "gain" of merging two encodings is how many bytes we save by doing so.
-    # save by merging it into another encoding. The "gain" of merging
-    # two encodings is how many bytes we save by doing so.
     #
     # High-level algorithm:
     #