--- a/layout/generic/CSSAlignUtils.h
+++ b/layout/generic/CSSAlignUtils.h
@@ -7,16 +7,18 @@
 
 #ifndef mozilla_CSSAlignUtils_h
 #define mozilla_CSSAlignUtils_h
 
 #include "mozilla/WritingModes.h"
 
 namespace mozilla {
 
+struct ReflowInput;
+
 class CSSAlignUtils {
 public:
   /**
    * Flags to customize the behavior of AlignJustifySelf:
    */
   enum class AlignJustifyFlags {
     eNoFlags           = 0,
     // Indicates that we have <overflow-position> = safe.

--- a/layout/generic/RubyUtils.h
+++ b/layout/generic/RubyUtils.h
@@ -4,16 +4,17 @@
  * 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/. */
 
 #ifndef mozilla_RubyUtils_h_
 #define mozilla_RubyUtils_h_
 
 #include "nsCSSAnonBoxes.h"
 #include "nsGkAtoms.h"
+#include "nsIFrame.h"
 #include "nsTArray.h"
 
 #define RTC_ARRAY_SIZE 1
 
 class nsRubyFrame;
 class nsRubyBaseFrame;
 class nsRubyTextFrame;
 class nsRubyContentFrame;

--- a/layout/generic/ScrollSnap.h
+++ b/layout/generic/ScrollSnap.h
@@ -1,16 +1,19 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 #ifndef mozilla_layout_ScrollSnap_h_
 #define mozilla_layout_ScrollSnap_h_
 
+#include "mozilla/Maybe.h"
+#include "nsIScrollableFrame.h"
+
 namespace mozilla {
 
 namespace layers {
 struct ScrollSnapInfo;
 }
 
 struct ScrollSnapUtils {
   /**