Add an extra data field to ParserContext.

This will be used for passing Gecko-specific information through
the CSS parser in stylo.

components/style/parser.rs

@@ -9,16 +9,38 @@ use selectors::parser::ParserContext as SelectorParserContext;
 use stylesheets::Origin;
 use url::Url;
 
+#[cfg(not(feature = "gecko"))]
+pub struct ParserContextExtraData;
+
+#[cfg(feature = "gecko")]
+pub struct ParserContextExtraData {
+}
+
+impl ParserContextExtraData {
+    #[cfg(not(feature = "gecko"))]
+    pub fn default() -> ParserContextExtraData {
+        ParserContextExtraData
+    }
+
+    #[cfg(feature = "gecko")]
+    pub fn default() -> ParserContextExtraData {
+        ParserContextExtraData { }
+    }
+}
+
 pub struct ParserContext<'a> {
     pub stylesheet_origin: Origin,
     pub base_url: &'a Url,
     pub selector_context: SelectorParserContext,
     pub error_reporter: Box<ParseErrorReporter + Send>,
+    pub extra_data: ParserContextExtraData,
 }
 
 impl<'a> ParserContext<'a> {
-    pub fn new(stylesheet_origin: Origin, base_url: &'a Url, error_reporter: Box<ParseErrorReporter + Send>)
-               -> ParserContext<'a> {
+    pub fn new_with_extra_data(stylesheet_origin: Origin, base_url: &'a Url,
+                               error_reporter: Box<ParseErrorReporter + Send>,
+                               extra_data: ParserContextExtraData)
+                               -> ParserContext<'a> {
         let mut selector_context = SelectorParserContext::new();
         selector_context.in_user_agent_stylesheet = stylesheet_origin == Origin::UserAgent;
         ParserContext {
@@ -26,8 +48,15 @@ impl<'a> ParserContext<'a> {
             base_url: base_url,
             selector_context: selector_context,
             error_reporter: error_reporter,
+            extra_data: extra_data,
         }
     }
+
+    pub fn new(stylesheet_origin: Origin, base_url: &'a Url, error_reporter: Box<ParseErrorReporter + Send>)
+               -> ParserContext<'a> {
+        let extra_data = ParserContextExtraData::default();
+        ParserContext::new_with_extra_data(stylesheet_origin, base_url, error_reporter, extra_data)
+    }
 }