Web Animations: Use an IDL enum for AnimationPlayState

BUG=396366

Review URL: https://codereview.chromium.org/562493002

git-svn-id: svn://svn.chromium.org/blink/trunk@181698 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/animation/AnimationPlayer.idl

@@ -28,6 +28,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+enum AnimationPlayState { "idle", "pending", "running", "paused", "finished" };
+
 [
     NoInterfaceObject,
     WillBeGarbageCollected,
@@ -37,7 +39,7 @@
     [RuntimeEnabled=WebAnimationsPlaybackControl]          attribute double     startTime;
     [RuntimeEnabled=WebAnimationsPlaybackControl]          attribute double     currentTime;
     [RuntimeEnabled=WebAnimationsPlaybackControl]          attribute double     playbackRate;
-    [RuntimeEnabled=WebAnimationsPlaybackControl] readonly attribute DOMString  playState;
+    [RuntimeEnabled=WebAnimationsPlaybackControl] readonly attribute AnimationPlayState playState;
     [RuntimeEnabled=WebAnimationsPlaybackControl, RaisesException] void finish();
     [RuntimeEnabled=WebAnimationsPlaybackControl] void play();
     [RuntimeEnabled=WebAnimationsPlaybackControl] void pause();