diff --git a/widget/gtk/CompositorWidgetParent.cpp b/widget/gtk/CompositorWidgetParent.cpp
--- a/widget/gtk/CompositorWidgetParent.cpp
+++ b/widget/gtk/CompositorWidgetParent.cpp
@@ -4,13 +4,13 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "CompositorWidgetParent.h"
 #include "mozilla/Unused.h"
 #include "mozilla/widget/PlatformWidgetTypes.h"
+#include "nsWindow.h"
 
-namespace mozilla {
-namespace widget {
+namespace mozilla::widget {
 
 CompositorWidgetParent::CompositorWidgetParent(
     const CompositorWidgetInitData& aInitData,
     const layers::CompositorOptions& aOptions)
     : GtkCompositorWidget(aInitData.get_GtkCompositorWidgetInitData(), aOptions,
@@ -49,7 +49,6 @@
     const uintptr_t& aXWindow, const bool& aShaped) {
   EnableRendering(aXWindow, aShaped);
   return IPC_OK();
 }
 
-}  // namespace widget
-}  // namespace mozilla
+}  // namespace mozilla::widget
diff --git a/widget/gtk/GtkCompositorWidget.cpp b/widget/gtk/GtkCompositorWidget.cpp
--- a/widget/gtk/GtkCompositorWidget.cpp
+++ b/widget/gtk/GtkCompositorWidget.cpp
@@ -3,10 +3,11 @@
  * 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/. */
 
 #include "GtkCompositorWidget.h"
 
+#include "mozilla/gfx/gfxVars.h"
 #include "mozilla/layers/CompositorThread.h"
 #include "mozilla/widget/InProcessCompositorWidget.h"
 #include "mozilla/widget/PlatformWidgetTypes.h"
 #include "nsWindow.h"
 
diff --git a/widget/gtk/IMContextWrapper.cpp b/widget/gtk/IMContextWrapper.cpp
--- a/widget/gtk/IMContextWrapper.cpp
+++ b/widget/gtk/IMContextWrapper.cpp
@@ -5,10 +5,11 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/Logging.h"
 #include "nsString.h"
 #include "prtime.h"
+#include "prenv.h"
 
 #include "IMContextWrapper.h"
 #include "nsGtkKeyUtils.h"
 #include "nsWindow.h"
 #include "mozilla/AutoRestore.h"
diff --git a/widget/gtk/InProcessGtkCompositorWidget.cpp b/widget/gtk/InProcessGtkCompositorWidget.cpp
--- a/widget/gtk/InProcessGtkCompositorWidget.cpp
+++ b/widget/gtk/InProcessGtkCompositorWidget.cpp
@@ -6,14 +6,14 @@
 #include "HeadlessCompositorWidget.h"
 #include "HeadlessWidget.h"
 #include "mozilla/widget/PlatformWidgetTypes.h"
 
 #include "InProcessGtkCompositorWidget.h"
+#include "VsyncDispatcher.h"
 #include "nsWindow.h"
 
-namespace mozilla {
-namespace widget {
+namespace mozilla::widget {
 
 /* static */
 RefPtr<CompositorWidget> CompositorWidget::CreateLocal(
     const CompositorWidgetInitData& aInitData,
     const layers::CompositorOptions& aOptions, nsIWidget* aWidget) {
@@ -39,7 +39,6 @@
           mWidget->GetCompositorVsyncDispatcher()) {
     cvd->SetCompositorVsyncObserver(aObserver);
   }
 }
 
-}  // namespace widget
-}  // namespace mozilla
+}  // namespace mozilla::widget
diff --git a/widget/gtk/MPRISServiceHandler.cpp b/widget/gtk/MPRISServiceHandler.cpp
--- a/widget/gtk/MPRISServiceHandler.cpp
+++ b/widget/gtk/MPRISServiceHandler.cpp
@@ -10,10 +10,11 @@
 #include <inttypes.h>
 #include <unordered_map>
 
 #include "MPRISInterfaceDescription.h"
 #include "mozilla/dom/MediaControlUtils.h"
+#include "mozilla/GRefPtr.h"
 #include "mozilla/GUniquePtr.h"
 #include "mozilla/UniquePtrExtensions.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Sprintf.h"
diff --git a/widget/gtk/WindowSurfaceX11.h b/widget/gtk/WindowSurfaceX11.h
--- a/widget/gtk/WindowSurfaceX11.h
+++ b/widget/gtk/WindowSurfaceX11.h
@@ -11,13 +11,13 @@
 
 #  include "mozilla/widget/WindowSurface.h"
 #  include "mozilla/gfx/Types.h"
 
 #  include <X11/Xlib.h>
+#  include "X11UndefineNone.h"
 
-namespace mozilla {
-namespace widget {
+namespace mozilla::widget {
 
 class WindowSurfaceX11 : public WindowSurface {
  public:
   WindowSurfaceX11(Display* aDisplay, Window aWindow, Visual* aVisual,
                    unsigned int aDepth);
@@ -31,10 +31,9 @@
   Visual* const mVisual;
   const unsigned int mDepth;
   const gfx::SurfaceFormat mFormat;
 };
 
-}  // namespace widget
-}  // namespace mozilla
+}  // namespace mozilla::widget
 
 #endif  // MOZ_X11
 #endif  // _MOZILLA_WIDGET_GTK_WINDOW_SURFACE_X11_H
diff --git a/widget/gtk/WindowSurfaceX11.cpp b/widget/gtk/WindowSurfaceX11.cpp
--- a/widget/gtk/WindowSurfaceX11.cpp
+++ b/widget/gtk/WindowSurfaceX11.cpp
@@ -4,14 +4,12 @@
  * 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/. */
 
 #include "WindowSurfaceX11.h"
 #include "gfxPlatform.h"
-#include "X11UndefineNone.h"
 
-namespace mozilla {
-namespace widget {
+namespace mozilla::widget {
 
 WindowSurfaceX11::WindowSurfaceX11(Display* aDisplay, Window aWindow,
                                    Visual* aVisual, unsigned int aDepth)
     : mDisplay(aDisplay),
       mWindow(aWindow),
@@ -44,7 +42,6 @@
   }
 
   return gfx::SurfaceFormat::UNKNOWN;
 }
 
-}  // namespace widget
-}  // namespace mozilla
+}  // namespace mozilla::widget
diff --git a/widget/gtk/nsApplicationChooser.cpp b/widget/gtk/nsApplicationChooser.cpp
--- a/widget/gtk/nsApplicationChooser.cpp
+++ b/widget/gtk/nsApplicationChooser.cpp
@@ -9,10 +9,11 @@
 
 #include "nsApplicationChooser.h"
 #include "WidgetUtils.h"
 #include "nsIMIMEInfo.h"
 #include "nsIWidget.h"
+#include "nsIFile.h"
 #include "nsCExternalHandlerService.h"
 #include "nsComponentManagerUtils.h"
 #include "nsGtkUtils.h"
 #include "nsPIDOMWindow.h"
 
diff --git a/widget/gtk/nsClipboard.cpp b/widget/gtk/nsClipboard.cpp
--- a/widget/gtk/nsClipboard.cpp
+++ b/widget/gtk/nsClipboard.cpp
@@ -29,10 +29,11 @@
 #include "nsStringStream.h"
 #include "nsIFileURL.h"
 #include "nsIObserverService.h"
 #include "mozilla/Services.h"
 #include "mozilla/RefPtr.h"
+#include "mozilla/GRefPtr.h"
 #include "mozilla/SchedulerGroup.h"
 #include "mozilla/StaticPrefs_widget.h"
 #include "mozilla/TimeStamp.h"
 #include "WidgetUtilsGtk.h"
 
diff --git a/widget/gtk/nsGtkKeyUtils.h b/widget/gtk/nsGtkKeyUtils.h
--- a/widget/gtk/nsGtkKeyUtils.h
+++ b/widget/gtk/nsGtkKeyUtils.h
@@ -18,10 +18,11 @@
 #endif
 #ifdef MOZ_WAYLAND
 #  include <gdk/gdkwayland.h>
 #  include <xkbcommon/xkbcommon.h>
 #endif
+#include "X11UndefineNone.h"
 
 class nsWindow;
 
 namespace mozilla {
 namespace widget {