[parsing] Turn FLAG_lazy_inner_functions back on.

(The bug below is fixed.)

BUG=v8:5938

Change-Id: Ifa0213b1475b1f065238ffad77a03cdfdc49bd28
Reviewed-on: https://chromium-review.googlesource.com/441724Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43142}

src/flag-definitions.h

@@ -902,7 +902,7 @@ DEFINE_BOOL(trace_maps, false, "trace map creation")
 DEFINE_BOOL(allow_natives_syntax, false, "allow natives syntax")
 DEFINE_BOOL(trace_parse, false, "trace parsing and preparsing")
 DEFINE_BOOL(trace_preparse, false, "trace preparsing decisions")
-DEFINE_BOOL(lazy_inner_functions, false, "enable lazy parsing inner functions")
+DEFINE_BOOL(lazy_inner_functions, true, "enable lazy parsing inner functions")
 DEFINE_BOOL(aggressive_lazy_inner_functions, false,
             "even lazier inner function parsing")
 DEFINE_IMPLICATION(aggressive_lazy_inner_functions, lazy_inner_functions)