Enable Cell-based prototype chain checks

Review URL: https://codereview.chromium.org/1070253004

Cr-Commit-Position: refs/heads/master@{#27872}

src/flag-definitions.h

@@ -676,7 +676,7 @@ DEFINE_INT(random_seed, 0,
 DEFINE_BOOL(trace_weak_arrays, false, "trace WeakFixedArray usage")
 DEFINE_BOOL(track_prototype_users, false,
             "keep track of which maps refer to a given prototype object")
-DEFINE_BOOL(eliminate_prototype_chain_checks, false,
+DEFINE_BOOL(eliminate_prototype_chain_checks, true,
             "collapse prototype chain checks into single-cell checks")
 DEFINE_IMPLICATION(eliminate_prototype_chain_checks, track_prototype_users)
 DEFINE_BOOL(use_verbose_printer, true, "allows verbose printing")