WebVTT: Support 'auto' text position

Source/core/html/track/vtt/VTTCue.idl

Index: Source/core/html/track/vtt/VTTCue.idl
diff --git a/Source/core/html/track/vtt/VTTCue.idl b/Source/core/html/track/vtt/VTTCue.idl
index 3ca0307dfa3833e35322b1a45a7ae1140a27cb27..6c133c021eb7f2c54147f6fd737b5aa404fde685 100644
--- a/Source/core/html/track/vtt/VTTCue.idl
+++ b/Source/core/html/track/vtt/VTTCue.idl
@@ -27,6 +27,7 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+enum AutoKeyword { "auto" };
 enum DirectionSetting { "" /* horizontal */, "rl", "lr" };
 enum AlignSetting { "start", "middle", "end", "left", "right" };
 
@@ -39,7 +40,8 @@ enum AlignSetting { "start", "middle", "end", "left", "right" };
     attribute DirectionSetting vertical;
     attribute boolean snapToLines;
     [RaisesException=Setter] attribute long line;

[philipj_slow, 2015/01/15 09:08:57]

How about line and size? I think grouping the long->double in line/position/size
into one CL and the introduction of AutoKeyword for line/position in another one
would make the most sense. Probably long->double as the first CL will be
cleanest.

[fs, 2015/01/15 10:07:16]

Yes, I was thinking about that too... I guess this goes together with the
comment about double vs. float representable values, as it begs the question of
internal representation.
As for AutoKeyword I guess 'line' could be folded into this CL since it should
be mostly trivial since algorithm part is implemented already - but the
test-changes might be daunting enough to warrant a split (I think I'd prefer the
split approach there). Thoughts?

[philipj_slow, 2015/01/19 14:44:26]

Split it is!

-    [RaisesException=Setter] attribute long position;
+    // FIXME: DOMString should be AutoKeyword. (crbug.com/240176)

[philipj_slow, 2015/01/15 09:08:57]

Can you comment on the bug so that this specific case can be prioritized?

[fs, 2015/01/15 10:07:16]

I added a comment in the "IDL status" doc, and bashi said he'd added it to his
list.

[philipj_slow, 2015/01/19 14:44:26]

Thanks!

[fs, 2015/01/19 15:09:06]

(This is now supported, so expect this FIXME to disappear when I upload the next
PS.)

+    [RaisesException=Setter] attribute (double or DOMString) position;

[philipj_slow, 2015/01/15 09:08:57]

Can you also add TypeChecking=Unrestricted to the interface and test what
happens when you set cue.position = Infinity/NaN?

[fs, 2015/01/15 10:07:16]

Good catch.

     [RaisesException=Setter] attribute long size;
     attribute AlignSetting align;
     attribute DOMString text;