Revert "Temporarily unship constant field tracking"

This reverts commit 4950dec7.

Reason for revert: Breaks on stress_background_compile variant https://logs.chromium.org/logs/v8/buildbucket/cr-buildbucket.appspot.com/8920804687849034208/+/steps/Mjsunit/0/logs/number-divide/0

Original change's description:
> Temporarily unship constant field tracking
> 
> This is to get better handle on improvements and regressions.
> 
> Bug: v8:8361, chromium:930680
> Change-Id: I2963b55f3480036ada885267a277a95d24a67656
> Reviewed-on: https://chromium-review.googlesource.com/c/1482737
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59800}

TBR=jarin@chromium.org,ishell@chromium.org

Change-Id: Ibf38c9cb2bf0921b7d93972a1e6cdd4c3d57c592
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:8361, chromium:930680
Reviewed-on: https://chromium-review.googlesource.com/c/1483610Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59801}

src/flag-definitions.h

@@ -1001,9 +1001,9 @@ DEFINE_BOOL(trace_ic, false,
 DEFINE_IMPLICATION(trace_ic, log_code)
 DEFINE_INT(ic_stats, 0, "inline cache state transitions statistics")
 DEFINE_VALUE_IMPLICATION(trace_ic, ic_stats, 1)
-DEFINE_BOOL_READONLY(track_constant_fields, false,
+DEFINE_BOOL_READONLY(track_constant_fields, true,
                      "enable constant field tracking")
-DEFINE_BOOL_READONLY(modify_map_inplace, false, "enable in-place map updates")
+DEFINE_BOOL_READONLY(modify_map_inplace, true, "enable in-place map updates")
 DEFINE_BOOL_READONLY(fast_map_update, false,
                      "enable fast map update by caching the migration target")
 DEFINE_INT(max_polymorphic_map_count, 4,