[heap] Enable incremental marking of wrappers

BUG=chromium:468240
NOTRY=true

Review-Url: https://codereview.chromium.org/2498343002
Cr-Commit-Position: refs/heads/master@{#40991}

src/flag-definitions.h

@@ -729,7 +729,7 @@ DEFINE_BOOL(age_code, true,
             "track un-executed functions to age code and flush only "
             "old code (required for code flushing)")
 DEFINE_BOOL(incremental_marking, true, "use incremental marking")
-DEFINE_BOOL(incremental_marking_wrappers, false,
+DEFINE_BOOL(incremental_marking_wrappers, true,
             "use incremental marking for marking wrappers")
 DEFINE_INT(min_progress_during_incremental_marking_finalization, 32,
            "keep finalizing incremental marking as long as we discover at "