diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index f0fa2fab899..496a75b0cc3 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -1034,7 +1034,6 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             }
         }
 
-        // TODO(gw): Support zoom (WR issue #28).
         if let Some(combined_event) = last_combined_event {
             let scroll_location = match combined_event.scroll_location {
                 ScrollLocation::Delta(delta) => {
diff --git a/components/layout/block.rs b/components/layout/block.rs
index 1f01327a160..f1ef7aa9423 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -794,7 +794,6 @@ impl BlockFlow {
                 self.base.floats = Floats::new(self.fragment.style.writing_mode);
             }
 
-            let mut margin_collapse_info = MarginCollapseInfo::new();
             let writing_mode = self.base.floats.writing_mode;
             self.base.floats.translate(LogicalSize::new(
                 writing_mode, -self.fragment.inline_start_offset(), Au(0)));
@@ -807,7 +806,7 @@ impl BlockFlow {
                 margins_may_collapse == MarginsMayCollapseFlag::MarginsMayCollapse &&
                 !self.base.flags.contains(FlowFlags::IS_ABSOLUTELY_POSITIONED) &&
                 self.fragment.border_padding.block_start == Au(0);
-            margin_collapse_info.initialize_block_start_margin(
+            let mut margin_collapse_info = MarginCollapseInfo::initialize_block_start_margin(
                 &self.fragment,
                 can_collapse_block_start_margin_with_kids);
 
diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index e544567250c..03dbf86fe97 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -3566,8 +3566,6 @@ impl InlineFlowDisplayListBuilding for InlineFlow {
     }
 
     fn build_display_list_for_inline(&mut self, state: &mut DisplayListBuildState) {
-        // TODO(#228): Once we form lines and have their cached bounds, we can be smarter and
-        // not recurse on a line if nothing in it can intersect the dirty region.
         debug!(
             "Flow: building display list for {} inline fragments",
             self.fragments.len()
diff --git a/components/layout/model.rs b/components/layout/model.rs
index 9d0d4c69926..d5b85a7424e 100644
--- a/components/layout/model.rs
+++ b/components/layout/model.rs
@@ -111,25 +111,21 @@ pub struct MarginCollapseInfo {
 }
 
 impl MarginCollapseInfo {
-    /// TODO(#2012, pcwalton): Remove this method once `fragment` is not an `Option`.
-    pub fn new() -> MarginCollapseInfo {
+    pub fn initialize_block_start_margin(
+        fragment: &Fragment,
+        can_collapse_block_start_margin_with_kids: bool,
+    ) -> MarginCollapseInfo {
         MarginCollapseInfo {
-            state: MarginCollapseState::AccumulatingCollapsibleTopMargin,
-            block_start_margin: AdjoiningMargins::new(),
+            state: if can_collapse_block_start_margin_with_kids {
+                MarginCollapseState::AccumulatingCollapsibleTopMargin
+            } else {
+                MarginCollapseState::AccumulatingMarginIn
+            },
+            block_start_margin: AdjoiningMargins::from_margin(fragment.margin.block_start),
             margin_in: AdjoiningMargins::new(),
         }
     }
 
-    pub fn initialize_block_start_margin(&mut self,
-                                         fragment: &Fragment,
-                                         can_collapse_block_start_margin_with_kids: bool) {
-        if !can_collapse_block_start_margin_with_kids {
-            self.state = MarginCollapseState::AccumulatingMarginIn
-        }
-
-        self.block_start_margin = AdjoiningMargins::from_margin(fragment.margin.block_start)
-    }
-
     pub fn finish_and_compute_collapsible_margins(mut self,
                                                   fragment: &Fragment,
                                                   containing_block_size: Option<Au>,