VTTCue: Support 'auto' for line

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

Index: Source/core/html/track/vtt/VTTCue.h
diff --git a/Source/core/html/track/vtt/VTTCue.h b/Source/core/html/track/vtt/VTTCue.h
index 4bd268803f0e11839074fbd0b49691384525c235..a29f43a0eb341b79503df47a9d701c5ffae53abf 100644
--- a/Source/core/html/track/vtt/VTTCue.h
+++ b/Source/core/html/track/vtt/VTTCue.h
@@ -36,6 +36,7 @@
 namespace blink {
 
 class Document;
+class DoubleOrAutoKeyword;
 class ExecutionContext;
 class VTTCue;
 class VTTScanner;
@@ -76,8 +77,8 @@ public:
     bool snapToLines() const { return m_snapToLines; }
     void setSnapToLines(bool);
 
-    double line() const { return m_linePosition; }
-    void setLine(double, ExceptionState&);
+    void line(DoubleOrAutoKeyword&) const;
+    void setLine(const DoubleOrAutoKeyword&);
 
     double position() const { return m_textPosition; }
     void setPosition(double, ExceptionState&);
@@ -188,6 +189,7 @@ private:
     FloatPoint m_displayPosition;
 
     bool m_snapToLines : 1;
+    bool m_lineIsAuto : 1;

[philipj_slow, 2015/01/20 14:52:31]

How about using NaN for auto? Too clever?

[fs, 2015/01/20 16:35:16]

I considered it, but since this is equally "free" storage-wise and felt slightly
more readable in places (since we can't compare NaN == NaN in the setter for
instance). that way certainly has it's allure though, so I'll code it up and see
what I think in practice...

Uploaded as PS3 for your viewing pleasure.

     bool m_displayTreeShouldChange : 1;
     bool m_notifyRegion : 1;
 };