VTTCue: Support 'auto' for line

LayoutTests/media/track/track-cue-mutable.html

Index: LayoutTests/media/track/track-cue-mutable.html
diff --git a/LayoutTests/media/track/track-cue-mutable.html b/LayoutTests/media/track/track-cue-mutable.html
index 698bfb88f8cd0c45fcbc7bd8da2de11d5820aa9c..decac851edbb320c54c280a87943093606c885c2 100644
--- a/LayoutTests/media/track/track-cue-mutable.html
+++ b/LayoutTests/media/track/track-cue-mutable.html
@@ -28,7 +28,7 @@
                 testExpected("textCue.pauseOnExit", false);
                 testExpected("textCue.vertical", "");
                 testExpected("textCue.snapToLines", true);
-                testExpected("textCue.line", -1);
+                testExpected("textCue.line", "auto");
                 testExpected("textCue.position", 50);
                 testExpected("textCue.size", 100);
                 testExpected("textCue.align", "middle");
@@ -57,13 +57,17 @@
                 run("textCue.snapToLines = false");
                 testExpected("textCue.snapToLines", false);
 
-                logSpecURL("http://www.whatwg.org/specs/web-apps/current-work/multipage/the-video-element.html#dom-texttrackcue-line",
-                            "On setting, if the text track cue snap-to-lines flag is not set, and the new value is negative or greater than 100, then throw an IndexSizeError exception.");
-                testDOMException("textCue.line = -2", "DOMException.INDEX_SIZE_ERR");
-                testDOMException("textCue.line = 102", "DOMException.INDEX_SIZE_ERR");
-                testExpected("textCue.line", -1);
+                logSpecURL("http://dev.w3.org/html5/webvtt/#dfn-vttcue-line",
+                           "On setting, the text track cue line position must be set to the new value; if the new value is the string 'auto', then it must be interpreted as the special value auto.");
+                testExpected("textCue.line", "auto");
+                testException("textCue.line = 'gazonk'", '"TypeError: Failed to set the \'line\' property on \'VTTCue\': \'gazonk\' is not a valid enum value."');
+                testExpected("textCue.line", "auto");
                 run("textCue.line = 42");
                 testExpected("textCue.line", 42);
+                run("textCue.line = -2");
+                testExpected("textCue.line", -2);
+                run("textCue.line = 102");
+                testExpected("textCue.line", 102);
                 run("textCue.snapToLines = true");
                 run("textCue.line = -2");
                 testExpected("textCue.line", -2);