Revert "[runtime] Deprecate old prototype maps"

This reverts commit 8974b75b.

Reason for revert: In hindsight, the CL made only partially sense and causes unnecessary IC-misses.

Original change's description:
> [runtime] Deprecate old prototype maps
> 
> Bug: chromium:757199
> Change-Id: I5936fab1784ebf8de6eddd3b2bec0e2cf1b73f82
> Reviewed-on: https://chromium-review.googlesource.com/632317
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47581}

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

Change-Id: I9f43a5f8c5242f575346f47c24377dd832eeccd1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:757199
Reviewed-on: https://chromium-review.googlesource.com/634906Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47594}

src/feedback-vector.cc

@@ -728,7 +728,6 @@ int FeedbackNexus::ExtractMaps(MapHandles* maps) const {
       WeakCell* cell = WeakCell::cast(array->get(i));
       if (!cell->cleared()) {
         Map* map = Map::cast(cell->value());
-        if (map->is_deprecated()) continue;
         maps->push_back(handle(map, isolate));
         found++;
       }
@@ -738,7 +737,6 @@ int FeedbackNexus::ExtractMaps(MapHandles* maps) const {
     WeakCell* cell = WeakCell::cast(feedback);
     if (!cell->cleared()) {
       Map* map = Map::cast(cell->value());
-      if (map->is_deprecated()) return 0;
       maps->push_back(handle(map, isolate));
       return 1;
     }

src/objects.cc

@@ -9188,7 +9188,6 @@ Handle<Map> Map::CopyReplaceDescriptors(
     }
   } else {
     result->InitializeDescriptors(*descriptors, *layout_descriptor);
-    map->deprecate();
   }
 #if V8_TRACE_MAPS
   if (FLAG_trace_maps &&

test/mjsunit/regress/regress-crbug-757199.js

-// Copyright 2017 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Flags: --allow-natives-syntax
-
-var obj1 = {};
-var obj2 = {};
-
-function h() {}
-
-h.prototype = obj2;
-
-function g(v) {
-  v.constructor;
-}
-function f() {
-  g(obj1);
-}
-
-obj1.x = 0;
-f();
-
-obj1.__defineGetter__("x", function() {});
-
-g(obj2);
-
-obj2.y = 0;
-
-%OptimizeFunctionOnNextCall(f);
-f();