Force layout to make a track rendering test non-flaky

LayoutTests/media/track/track-cue-container-rendering-position.html

Index: LayoutTests/media/track/track-cue-container-rendering-position.html
diff --git a/LayoutTests/media/track/track-cue-container-rendering-position.html b/LayoutTests/media/track/track-cue-container-rendering-position.html
index 2167967d1c8bfb56b10e114d26b8cc8ff179c6ab..30c02df8b71e307f58f18907aecb2de8bf8f3ce5 100644
--- a/LayoutTests/media/track/track-cue-container-rendering-position.html
+++ b/LayoutTests/media/track/track-cue-container-rendering-position.html
@@ -20,6 +20,7 @@
 
             consoleWrite("");
             cueDisplayElement = textTrackDisplayElement(video, 'display', 0);
+            document.body.offsetTop; // Force layout.
             testExpected("cueDisplayElement.offsetTop > (video.videoHeight * .75)", true);

[fs, 2014/09/03 10:33:02]

Any idea why reading cueDisplayElement.offsetTop is not sufficient?

[philipj_slow, 2014/09/03 11:31:55]

While debugging I replaced it with a constant and that passed consistently with
the forced layout. I'm guessing that font rendering differences will cause it to
be slightly different on different platforms, but didn't investigate further.

             endTest();
         }