diff --git a/components/style/gecko/snapshot.rs b/components/style/gecko/snapshot.rs
index 08d5288a8d0..4398fbf8e29 100644
--- a/components/style/gecko/snapshot.rs
+++ b/components/style/gecko/snapshot.rs
@@ -2,6 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+//! A gecko snapshot, that stores the element attributes and state before they
+//! change in order to properly calculate restyle hints.
+
 use element_state::ElementState;
 use gecko::snapshot_helpers;
 use gecko::wrapper::{AttrSelectorHelpers, GeckoElement};
@@ -14,6 +17,10 @@ use selectors::parser::AttrSelector;
 use std::ptr;
 use string_cache::Atom;
 
+/// A snapshot of a Gecko element.
+///
+/// This is really a Gecko type (see `ServoElementSnapshot.h` in Gecko) we wrap
+/// here.
 #[derive(Debug)]
 pub struct GeckoElementSnapshot(bindings::ServoElementSnapshotOwned);
 
@@ -30,14 +37,17 @@ impl Drop for GeckoElementSnapshot {
 }
 
 impl GeckoElementSnapshot {
+    /// Create a new snapshot of the given element.
     pub fn new<'le>(el: GeckoElement<'le>) -> Self {
         unsafe { GeckoElementSnapshot(bindings::Gecko_CreateElementSnapshot(el.0)) }
     }
 
+    /// Get a mutable reference to the snapshot.
     pub fn borrow_mut_raw(&mut self) -> bindings::ServoElementSnapshotBorrowedMut {
         &mut *self.0
     }
 
+    /// Get the pointer to the actual snapshot.
     pub fn ptr(&self) -> *const ServoElementSnapshot {
         &*self.0
     }
@@ -152,7 +162,6 @@ impl ElementSnapshot for GeckoElementSnapshot {
         }
     }
 
-    // TODO: share logic with Element::{has_class, each_class}?
     fn has_class(&self, name: &Atom) -> bool {
         snapshot_helpers::has_class(self.ptr(),
                                     name,
diff --git a/components/style/gecko/snapshot_helpers.rs b/components/style/gecko/snapshot_helpers.rs
index ee7fdd14421..9216c92cd2f 100644
--- a/components/style/gecko/snapshot_helpers.rs
+++ b/components/style/gecko/snapshot_helpers.rs
@@ -8,8 +8,12 @@ use gecko_bindings::structs::nsIAtom;
 use std::{ptr, slice};
 use string_cache::Atom;
 
+/// A function that, given an element of type `T`, allows you to get a single
+/// class or a class list.
 pub type ClassOrClassList<T> = unsafe extern fn (T, *mut *mut nsIAtom, *mut *mut *mut nsIAtom) -> u32;
 
+/// Given an item `T`, a class name, and a getter function, return whether that
+/// element has the class that `name` represents.
 pub fn has_class<T>(item: T,
                     name: &Atom,
                     getter: ClassOrClassList<T>) -> bool
@@ -30,6 +34,8 @@ pub fn has_class<T>(item: T,
 }
 
 
+/// Given an item, a callback, and a getter, execute `callback` for each class
+/// this `item` has.
 pub fn each_class<F, T>(item: T,
                         mut callback: F,
                         getter: ClassOrClassList<T>)