Improve acid2. Fix line height calculation. Text fragments get correct enclosing element style.

* Enabled acid2 on mac + linux. Updated the reference image. The only difference from the
real acid2 now is the paint order and a 1 pixel horizontal offset on the nose.
* Change line-height to be calculated correctly.
* Apply enclosing element style to text fragments.

components/layout/table_wrapper.rs

@@ -244,6 +244,10 @@ impl Flow for TableWrapperFlow {
         self
     }
 
+    fn as_immutable_table_wrapper<'a>(&'a self) -> &'a TableWrapperFlow {
+        self
+    }
+
     fn as_block<'a>(&'a mut self) -> &'a mut BlockFlow {
         &mut self.block_flow
     }