Rework float value/percentage scanning for VTTRegion

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

Index: Source/core/html/track/vtt/VTTScanner.h
diff --git a/Source/core/html/track/vtt/VTTScanner.h b/Source/core/html/track/vtt/VTTScanner.h
index 89d7e7d955e3878e4553e8e049e5c35495e1a8e9..56078b53fe848ebbaeeac7532711e64707b59b53 100644
--- a/Source/core/html/track/vtt/VTTScanner.h
+++ b/Source/core/html/track/vtt/VTTScanner.h
@@ -126,6 +126,9 @@ public:
     // Note: Does not handle sign.
     unsigned scanDigits(int& number);
 
+    // Scan a floating point value on one of the forms: \d+\.? \d+\.\d+ \.\d+

[Mike West, 2014/01/21 07:59:24]

Is "0." a valid floating point value? It doesn't seem like it should be, but
maybe there's a good reason for that strangeness?

[fs, 2014/01/21 08:19:57]

It is a valid floating point value. (Compare to other definitions - like C++
[2.13.3]).

+    bool scanFloat(float& number);
+
 protected:
     Position position() const { return m_data.characters8; }
     Position end() const { return m_end.characters8; }