Always notify the MediaPlayer of any seek.

LayoutTests/media/media-controller-effective-playback-rate.html

Index: LayoutTests/media/media-controller-effective-playback-rate.html
diff --git a/LayoutTests/media/media-controller-effective-playback-rate.html b/LayoutTests/media/media-controller-effective-playback-rate.html
index e0d28631db9727e37d01066e75ea2a994524a62c..a8d1bfcdcafa5fb7512a0a2ef9e4dc260862a5a1 100644
--- a/LayoutTests/media/media-controller-effective-playback-rate.html
+++ b/LayoutTests/media/media-controller-effective-playback-rate.html
@@ -13,7 +13,7 @@
                 // Set the rate on the media element so playback won't move forward.
                 video.playbackRate = 0;
 
-                waitForEvent("canplay",canplay);
+                waitForEventOnce("canplay",canplay);
             };
 
             var canplay = function()
@@ -33,6 +33,10 @@
 
             var play = function()
             {
+                waitForEventOnce("playing", playing);
+            };
+
+            var playing = function() {
                 waitForEventOnce("timeupdate", timeupdate);
             };