[heap] Reland uncommit unused large object page memory.

test/mjsunit/regress/regress-617882.js

+// Copyright 2016 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: --invoke-weak-callbacks --omit-quit --gc-interval=355 --expose-debug-as=debug
+
+var __v_33 = {};
+__v_4 = 70000;
+function __f_18() {
+  if ((__v_7 % 50) != 0) {
+  } else {
+    return __v_33 + 0.5;
+  }
+}
+function __f_17(a) {
+  for (var __v_7= 0; __v_7 < __v_4; ++__v_7 ) {
+    a[__v_7] = __f_18();
+  }
+}
+for (var __v_7= 0; __v_7 < __v_4; __v_7 += 500 ) {
+}
+__v_9 = new Array();
+__f_17(__v_9);
+__v_9.length = 100;
+Debug = debug.Debug
+function __f_26() {
+      }
+__v_29 = "(function() {\
+         })()";