fix some possible problems related multiple global copies of core-js,

#880

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Fixed microtask implementation in engines with `MutationObserver`, but without `document`, [#865](https://github.com/zloirock/core-js/issues/865), [#866](https://github.com/zloirock/core-js/issues/866)
 - Fixed `core-js-builder` with an empty (after the targets engines or another filtration) modules list, [#822](https://github.com/zloirock/core-js/issues/822)
 - Fixed possible twice call of `window.onunhandledrejection`, [#760](https://github.com/zloirock/core-js/issues/760)
+- Fixed some possible problems related multiple global copies of `core-js`, [#880](https://github.com/zloirock/core-js/issues/880)
 - Added a workaround for 3rd party `Reflect.set` polyfill bug, [#847](https://github.com/zloirock/core-js/issues/847)
 - Forced replacement of `Array#{ reduce, reduceRight }` in Chrome 80-82 because of [a bug](https://bugs.chromium.org/p/chromium/issues/detail?id=1049982), [#766](https://github.com/zloirock/core-js/issues/766)
 - Updated compat data:

packages/core-js/internals/internal-state.js

@@ -3,6 +3,7 @@ var global = require('../internals/global');
 var isObject = require('../internals/is-object');
 var createNonEnumerableProperty = require('../internals/create-non-enumerable-property');
 var objectHas = require('../internals/has');
+var shared = require('../internals/shared-store');
 var sharedKey = require('../internals/shared-key');
 var hiddenKeys = require('../internals/hidden-keys');
 
@@ -23,7 +24,7 @@ var getterFor = function (TYPE) {
 };
 
 if (NATIVE_WEAK_MAP) {
-  var store = new WeakMap();
+  var store = shared.state || (shared.state = new WeakMap());
   var wmget = store.get;
   var wmhas = store.has;
   var wmset = store.set;