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@@ -615,15 +615,20 @@ var Reveal = (function(){
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if( config.focusBodyOnPageVisiblityChange ) {
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var visibilityChange;
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- if ('hidden' in document) {
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+
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+ if( 'hidden' in document ) {
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visibilityChange = 'visibilitychange';
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- } else if ('msHidden' in document) {
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+ }
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+ else if( 'msHidden' in document ) {
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visibilityChange = 'msvisibilitychange';
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- } else if ('webkitHidden' in document) {
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+ }
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+ else if( 'webkitHidden' in document ) {
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visibilityChange = 'webkitvisibilitychange';
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}
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- document.addEventListener(visibilityChange, onPageVisibilityChange, false);
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+ if( visibilityChange ) {
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+ document.addEventListener( visibilityChange, onPageVisibilityChange, false );
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+ }
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}
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[ 'touchstart', 'click' ].forEach( function( eventName ) {
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