TracMercurial for 0.11: use `filelog.size`, which can give the size of a file in a much more efficient way than the naive `len(self.read())` used before, when revlogng is used. If revlogng is not used, `filelog.size()` reverts to the inefficient way, as that was the only way before revlogng. The other TracMercurial branch will not use this, so that it can remain compatible with old hg versions (0.8.1 and older).
