Specs: Allow for anonymous properties

sky/specs/style.md

 Sky Style Language
 ==================
 
 Planed changes
 --------------
 
 Add //-to-end-of-line comments to be consistent with the script
 language.
 
 
@@ skipping 342 matching lines @@
   any resolve(PropertyHandle property, RenderNode node, StyleValueResolverSettings? settings = null);
 }
 */
 
 class ObjectStyleValue : AbstractOpaqueStyleValue {
   constructor(StyleNode parentNode, any value);
     // calls superclass constructor
 }
 
 dictionary PropertySettings {
-  String name;
-  StyleGrammar grammar;
+  String? name = null; // null if the property can't be set from a <style> block
+  StyleGrammar? grammar = null; // msut be non-null if name is non-null; must be null otherwise
   Boolean inherited = false;
   any initialValue = null;
   Boolean needsManager = false;
   Boolean needsLayout = false;
   Boolean needsPaint = false;
   // PropertyHandle propertyHandle; // assigned by registerProperty
   // Integer dependencyBit; // assigned by StyleValueResolverSettings.dependsOn()
 }
 typedef PropertyHandle Integer;
 PropertyHandle registerProperty(PropertySettings propertySettings);
+  // registers a property with the given settings, and returns an integer >= 0
+  // that can be used to refer to this property
 
 // sky:core exports a bunch of style grammars so that people can extend them
 attribute StyleGrammar PositiveLengthOrInfinityStyleGrammar; // resolves to LengthStyleValue
 attribute StyleGrammar PositiveLengthOrAutoStyleGrammar; // resolves to LengthStyleValue or IdentifierStyleValue (with value 'auto')
 attribute StyleGrammar PositiveLengthStyleGrammar; // resolves to LengthStyleValue
 attribute StyleGrammar NumberGrammar; // resolves to NumericStyleValue
 attribute StyleGrammar ColorGrammar; // resolves to ColorStyleValue
 attribute StyleGrammar DisplayStyleGrammar; // resolves to ObjectStyleValue
 ```  
 
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 ```
 
 The ``div`` element doesn't have any default styles.
 
 These declarations are all shared between all the elements (so e.g. if
 you reach in and change the declaration that was added to a ``title``
 element, you're going to change the styles of all the other
 default-hidden elements). (In other words, in the code snippets above,
 the ``d`` variable is initialised in shared code, and only the
 addStyles() call is per-element.)