Re-enables the readability/fn_size presubmit.

BUG=

Review-Url: https://codereview.chromium.org/2601043002
Cr-Commit-Position: refs/heads/master@{#41969}

tools/presubmit.py

@@ -55,7 +55,6 @@ from testrunner.local import utils
 # build/include_what_you_use: Started giving false positives for variables
 #   named "string" and "map" assuming that you needed to include STL headers.
 # TODO(bmeurer): Fix and re-enable readability/check
-# TODO(epertoso): Maybe re-enable readability/fn_size after
 # http://crrev.com/2199323003 relands.
 
 LINT_RULES = """
@@ -63,7 +62,6 @@ LINT_RULES = """
 -build/include_what_you_use
 -build/namespaces
 -readability/check
--readability/fn_size
 +readability/streams
 -runtime/references
 """.split()