diff -r 000000000000 -r 6474c204b198 layout/style/MediaQueryList.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/style/MediaQueryList.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,95 @@
+/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+/* implements DOM interface for querying and observing media queries */
+
+#ifndef mozilla_dom_MediaQueryList_h
+#define mozilla_dom_MediaQueryList_h
+
+#include "nsISupports.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsAutoPtr.h"
+#include "nsTArray.h"
+#include "prclist.h"
+#include "mozilla/Attributes.h"
+#include "nsWrapperCache.h"
+#include "mozilla/dom/MediaQueryListBinding.h"
+
+class nsPresContext;
+class nsMediaList;
+
+namespace mozilla {
+namespace dom {
+
+class MediaQueryList MOZ_FINAL : public nsISupports,
+                                 public nsWrapperCache,
+                                 public PRCList
+{
+public:
+  // The caller who constructs is responsible for calling Evaluate
+  // before calling any other methods.
+  MediaQueryList(nsPresContext *aPresContext,
+                 const nsAString &aMediaQueryList);
+private:
+  ~MediaQueryList();
+
+public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(MediaQueryList)
+
+  nsISupports* GetParentObject() const;
+
+  struct HandleChangeData {
+    nsRefPtr<MediaQueryList> mql;
+    nsRefPtr<mozilla::dom::MediaQueryListListener> callback;
+  };
+
+  typedef FallibleTArray< nsRefPtr<mozilla::dom::MediaQueryListListener> > CallbackList;
+  typedef FallibleTArray<HandleChangeData> NotifyList;
+
+  // Appends listeners that need notification to aListenersToNotify
+  void MediumFeaturesChanged(NotifyList &aListenersToNotify);
+
+  bool HasListeners() const { return !mCallbacks.IsEmpty(); }
+
+  void RemoveAllListeners();
+
+  JSObject* WrapObject(JSContext* aCx) MOZ_OVERRIDE;
+
+  // WebIDL methods
+  void GetMedia(nsAString& aMedia);
+  bool Matches();
+  void AddListener(mozilla::dom::MediaQueryListListener& aListener);
+  void RemoveListener(mozilla::dom::MediaQueryListListener& aListener);
+
+private:
+  void RecomputeMatches();
+
+  // We only need a pointer to the pres context to support lazy
+  // reevaluation following dynamic changes.  However, this lazy
+  // reevaluation is perhaps somewhat important, since some usage
+  // patterns may involve the creation of large numbers of
+  // MediaQueryList objects which almost immediately become garbage
+  // (after a single call to the .matches getter).
+  //
+  // This pointer does make us a little more dependent on cycle
+  // collection.
+  //
+  // We have a non-null mPresContext for our entire lifetime except
+  // after cycle collection unlinking.  Having a non-null mPresContext
+  // is equivalent to being in that pres context's mDOMMediaQueryLists
+  // linked list.
+  nsRefPtr<nsPresContext> mPresContext;
+
+  nsRefPtr<nsMediaList> mMediaList;
+  bool mMatches;
+  bool mMatchesValid;
+  CallbackList mCallbacks;
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif /* !defined(mozilla_dom_MediaQueryList_h) */