Work around GC bug to fix flaky track tests

LayoutTests/media/track/track-remove-track.html

Index: LayoutTests/media/track/track-remove-track.html
diff --git a/LayoutTests/media/track/track-remove-track.html b/LayoutTests/media/track/track-remove-track.html
index 430ce9463c6d47465fa8aceed4c94db7787b1ab1..cddfb8434cb9d0066038d7298b5ad2055e189042 100644
--- a/LayoutTests/media/track/track-remove-track.html
+++ b/LayoutTests/media/track/track-remove-track.html
@@ -13,6 +13,8 @@
             async_test(function(test)
             {
                 var video = document.createElement("video");
+                // add to body to prevent GC pending http://crbug.com/400659
+                document.body.appendChild(video);
                 var track;
 
                 function trackRemoved()
@@ -39,6 +41,8 @@
             async_test(function(test)
             {
                 var video = document.createElement("video");
+                // add to body to prevent GC pending http://crbug.com/400659
+                document.body.appendChild(video);
 
                 // Create an out-of-band text track by adding a track element.
                 var trackElement = document.createElement('track');