layout: Implement ordered lists, CSS counters, and quotes per CSS 2.1

§ 12.3-12.5.

Only simple alphabetic and numeric counter styles are supported. (This
is most of them though.)

Although this PR adds a sequential pass to layout, I verified that on
pages that contain a reasonable number of ordered lists (Reddit
`/r/rust`), the time spent in generated content resolution is dwarfed by
the time spent in the parallelizable parts of layout. So I don't expect
this to negatively affect our parallelism expect perhaps in pathological
cases.

components/layout/table_wrapper.rs

@@ -13,13 +13,13 @@
 
 #![deny(unsafe_blocks)]
 
-use block::{BlockFlow, BlockNonReplaced, FloatNonReplaced, ISizeAndMarginsComputer, MarginsMayCollapseFlag};
-use construct::FlowConstructor;
+use block::{BlockFlow, BlockNonReplaced, FloatNonReplaced, ISizeAndMarginsComputer};
+use block::{MarginsMayCollapseFlag};
 use context::LayoutContext;
 use floats::FloatKind;
 use flow::{FlowClass, Flow, ImmutableFlowUtils};
 use flow::{IMPACTED_BY_LEFT_FLOATS, IMPACTED_BY_RIGHT_FLOATS};
-use fragment::{Fragment, FragmentBorderBoxIterator};
+use fragment::{Fragment, FragmentBorderBoxIterator, FragmentMutator};
 use table::{ColumnComputedInlineSize, ColumnIntrinsicInlineSize};
 use wrapper::ThreadSafeLayoutNode;
 
@@ -70,23 +70,6 @@ impl TableWrapperFlow {
         }
     }
 
-    pub fn from_node(constructor: &mut FlowConstructor,
-                     node: &ThreadSafeLayoutNode)
-                     -> TableWrapperFlow {
-        let mut block_flow = BlockFlow::from_node(constructor, node);
-        let table_layout = if block_flow.fragment().style().get_table().table_layout ==
-                              table_layout::T::fixed {
-            TableLayout::Fixed
-        } else {
-            TableLayout::Auto
-        };
-        TableWrapperFlow {
-            block_flow: block_flow,
-            column_intrinsic_inline_sizes: vec!(),
-            table_layout: table_layout
-        }
-    }
-
     pub fn float_from_node_and_fragment(node: &ThreadSafeLayoutNode,
                                         fragment: Fragment,
                                         float_kind: FloatKind)
@@ -383,6 +366,10 @@ impl Flow for TableWrapperFlow {
                                              stacking_context_position: &Point2D<Au>) {
         self.block_flow.iterate_through_fragment_border_boxes(iterator, stacking_context_position)
     }
+
+    fn mutate_fragments(&mut self, mutator: &mut FragmentMutator) {
+        self.block_flow.mutate_fragments(mutator)
+    }
 }
 
 impl fmt::Debug for TableWrapperFlow {