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							- /*
 
-  * Copyright 2020 Google LLC
 
-  *
 
-  * Licensed under the Apache License, Version 2.0 (the "License");
 
-  * you may not use this file except in compliance with the License.
 
-  * You may obtain a copy of the License at
 
-  *
 
-  *     https://www.apache.org/licenses/LICENSE-2.0
 
-  *
 
-  * Unless required by applicable law or agreed to in writing, software
 
-  * distributed under the License is distributed on an "AS IS" BASIS,
 
-  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 
-  * See the License for the specific language governing permissions and
 
-  * limitations under the License.
 
-  */
 
- let firstHiddenTime = document.visibilityState === 'hidden' ? 0 : Infinity;
 
- const onVisibilityChange = (event) => {
 
-     if (document.visibilityState === 'hidden') {
 
-         firstHiddenTime = event.timeStamp;
 
-         removeEventListener('visibilitychange', onVisibilityChange, true);
 
-     }
 
- };
 
- // Note: do not add event listeners unconditionally (outside of polyfills).
 
- addEventListener('visibilitychange', onVisibilityChange, true);
 
- export const getFirstHiddenTime = () => firstHiddenTime;
 
 
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