Fix($animateCss): should clear cache if element has no animation.

[sreeramu]

We should remove animation cache if the element don't have animation so follow-up animation on the same element will not be from cache.

This PR will close #12214 #12518

[sreeramu]

@matsko can you check this PR, is the fix is OK or is it not a issue.?

[matsko]

Hey @sreeramu. Thanks again for putting in work into fixing ngAnimate.

The cache needs to be cleared in the next RAF. The reason for this is if a big list of repeated items attempts to detect an animation then it will only perform the getComputedStyle detection code once. Once things are quiet then it clears the cache. The final code should look like this:

      function closeAndReturnNoopAnimator() {
        runner = new $$AnimateRunner({
          end: endFn,
          cancel: cancelFn
        });

        // this will clear the cache internally
        waitUntilQuiet(noop);
        close();

        return {
          $$willAnimate: false,
          start: function() {
            return runner;
          },
          end: endFn
        };
      }

That one line is all that needs to be changed. Then inside of your test code just add a call to $$rAF.flush() before running the next animation.

[sreeramu]

Thanks @matsko for explaining the issue clearly, i had updated the PR according to your comments.

[matsko]

Landed as 0a75a3d. Thank you @sreeramu.