npm_modules: Fork bower_components into Polymer 0.4.0 and 0.5.0 versions

polymer_0.4.0/bower_components/web-animations-js/test/testcases/test-reversed-player-active-phase.html

 <style>
 #target {
     position: absolute;
     width: 10px;
     height: 10px;
     background: black;
 }
 </style>
 <script src="../bootstrap.js"></script>
 <div id="target"></div>
 <script>
 timing_test(function() {
     var player = target.animate([{left: '0px'}, {left: '100px'}], {duration: 2, fill: 'forwards'});
 
     at(1, function() {
         assert_styles(target, {left: '50px'});
         player.currentTime = 3;
         player.playbackRate = -1;
         assert_styles(target, {left: '100px'});
     }, 'AnimationPlayer reversing');
 
     at(2, function() {}, 'Tick');
 
     at(3, function() {
         assert_styles(target, {left: '50px'});
     }, 'Reversed player entering its active phase should take effect');
 });
 </script>