Add layout tests for seeks to zero on streaming sources.

LayoutTests/http/tests/media/resources/load-video.php

Index: LayoutTests/http/tests/media/resources/load-video.php
diff --git a/LayoutTests/http/tests/media/resources/load-video.php b/LayoutTests/http/tests/media/resources/load-video.php
index 00a39f598c0a66b1c3006ae15d9bfae1cfa3db5d..8f0e8eb80366812905369844543c1d5570601ea0 100644
--- a/LayoutTests/http/tests/media/resources/load-video.php
+++ b/LayoutTests/http/tests/media/resources/load-video.php
@@ -2,10 +2,12 @@
 
     $fileName = $_GET["name"];
     $type = $_GET["type"];
+    $norange = $_GET["norange"];
 
     $_GET = array();
     $_GET['name'] = $fileName;
     $_GET['type'] = $type;
-    @include("./serve-video.php"); 
+    $_GET['norange'] = $norange;
+    @include("./serve-video.php");
 
 ?>