diff -up firefox-61.0/browser/base/content/browser.js.1424422 firefox-61.0/browser/base/content/browser.js
diff -up firefox-61.0/browser/base/content/browser-tabsintitlebar.js.1424422 firefox-61.0/browser/base/content/browser-tabsintitlebar.js
--- firefox-61.0/browser/base/content/browser-tabsintitlebar.js.1424422	2018-06-19 01:03:32.000000000 +0200
+++ firefox-61.0/browser/base/content/browser-tabsintitlebar.js	2018-06-20 14:59:44.121827553 +0200
@@ -36,6 +36,7 @@ var TabsInTitlebar = {
     window.addEventListener("resize", this);
 
     gDragSpaceObserver.init();
+    gLightThemeObserver.init();
 
     this._initialized = true;
     this.update();
@@ -302,6 +303,7 @@ var TabsInTitlebar = {
     this._menuObserver.disconnect();
     CustomizableUI.removeListener(this);
     gDragSpaceObserver.uninit();
+    gLightThemeObserver.uninit();
   }
 };
 
@@ -343,3 +345,21 @@ var gDragSpaceObserver = {
     TabsInTitlebar.update();
   },
 };
+
+var gLightThemeObserver = {
+  init() {
+    Services.obs.addObserver(this, "lightweight-theme-styling-update");
+  },
+
+  uninit() {
+    Services.obs.removeObserver(this, "lightweight-theme-styling-update");
+  },
+
+  observe(aSubject, aTopic, aData) {
+    switch (aTopic) {
+      case "lightweight-theme-styling-update":
+        TabsInTitlebar.updateAppearance(true);
+        break;
+    }
+  },
+};
diff -up firefox-61.0/browser/themes/linux/browser.css.1424422 firefox-61.0/browser/themes/linux/browser.css
--- firefox-61.0/browser/themes/linux/browser.css.1424422	2018-06-19 01:03:33.000000000 +0200
+++ firefox-61.0/browser/themes/linux/browser.css	2018-06-20 14:17:43.193681172 +0200
@@ -709,12 +709,20 @@ notification[value="translation"] menuli
   }
 
   @media (-moz-gtk-csd-maximize-button) {
-    #titlebar-max {
+    #titlebar-max:not(:-moz-lwtheme) {
       -moz-appearance: -moz-window-button-maximize;
     }
-    :root[sizemode="maximized"] #titlebar-max {
+    #titlebar-max:-moz-lwtheme {
+      -moz-appearance: none !important;
+      list-style-image: url(chrome://browser/skin/window-controls/maximize-themes.svg);
+    }
+    :root[sizemode="maximized"] #titlebar-max:not(:-moz-lwtheme) {
       -moz-appearance: -moz-window-button-restore;
     }
+    :root[sizemode="maximized"] #titlebar-max:-moz-lwtheme {
+      -moz-appearance: none !important;
+      list-style-image: url(chrome://browser/skin/window-controls/restore-themes.svg);
+    }
   }
   @media (-moz-gtk-csd-maximize-button: 0) {
     #titlebar-max {
@@ -723,9 +731,13 @@ notification[value="translation"] menuli
   }
 
   @media (-moz-gtk-csd-close-button) {
-    #titlebar-close {
+    #titlebar-close:not(:-moz-lwtheme) {
       -moz-appearance: -moz-window-button-close;
     }
+    #titlebar-close:-moz-lwtheme {
+      -moz-appearance: none !important;
+      list-style-image: url(chrome://browser/skin/window-controls/close-themes.svg);
+    }
   }
   @media (-moz-gtk-csd-close-button: 0) {
     #titlebar-close {
diff -up firefox-61.0/browser/themes/linux/jar.mn.1424422 firefox-61.0/browser/themes/linux/jar.mn
diff -up firefox-61.0/browser/themes/linux/window-controls/close-themes.svg.1424422 firefox-61.0/browser/themes/linux/window-controls/close-themes.svg
--- firefox-61.0/browser/themes/linux/window-controls/close-themes.svg.1424422	2018-06-20 14:17:43.194681169 +0200
+++ firefox-61.0/browser/themes/linux/window-controls/close-themes.svg	2018-06-20 14:17:43.194681169 +0200
@@ -0,0 +1,7 @@
+<!-- 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/. -->
+<svg width="12" height="12" xmlns="http://www.w3.org/2000/svg">
+  <path stroke="black" stroke-width="3.6" stroke-opacity=".75" d="M1,1 l 10,10 M1,11 l 10,-10"/>
+  <path stroke="white" stroke-width="1.9" d="M1.75,1.75 l 8.5,8.5 M1.75,10.25 l 8.5,-8.5"/>
+</svg>
diff -up firefox-61.0/browser/themes/linux/window-controls/maximize-themes.svg.1424422 firefox-61.0/browser/themes/linux/window-controls/maximize-themes.svg
--- firefox-61.0/browser/themes/linux/window-controls/maximize-themes.svg.1424422	2018-06-20 14:17:43.194681169 +0200
+++ firefox-61.0/browser/themes/linux/window-controls/maximize-themes.svg	2018-06-20 14:17:43.194681169 +0200
@@ -0,0 +1,7 @@
+<!-- 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/. -->
+<svg width="12" height="12" xmlns="http://www.w3.org/2000/svg" shape-rendering="crispEdges" fill="none">
+  <rect stroke="black" stroke-width="3.6" stroke-opacity=".75" x="2" y="2" width="8" height="8"/>
+  <rect stroke="white" stroke-width="1.9" x="2" y="2" width="8" height="8"/>
+</svg>
diff -up firefox-61.0/browser/themes/linux/window-controls/minimize-themes.svg.1424422 firefox-61.0/browser/themes/linux/window-controls/minimize-themes.svg
--- firefox-61.0/browser/themes/linux/window-controls/minimize-themes.svg.1424422	2018-06-20 14:17:43.194681169 +0200
+++ firefox-61.0/browser/themes/linux/window-controls/minimize-themes.svg	2018-06-20 14:17:43.194681169 +0200
@@ -0,0 +1,7 @@
+<!-- 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/. -->
+<svg width="12" height="12" xmlns="http://www.w3.org/2000/svg" shape-rendering="crispEdges">
+  <line stroke="black" stroke-width="3.6" stroke-opacity=".75" x1="0" y1="6" x2="12" y2="6"/>
+  <line stroke="white" stroke-width="1.9" x1="1" y1="6" x2="11" y2="6"/>
+</svg>
diff -up firefox-61.0/browser/themes/linux/window-controls/restore-themes.svg.1424422 firefox-61.0/browser/themes/linux/window-controls/restore-themes.svg
--- firefox-61.0/browser/themes/linux/window-controls/restore-themes.svg.1424422	2018-06-20 14:17:43.194681169 +0200
+++ firefox-61.0/browser/themes/linux/window-controls/restore-themes.svg	2018-06-20 14:17:43.194681169 +0200
@@ -0,0 +1,8 @@
+<!-- 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/. -->
+<svg width="12" height="12" xmlns="http://www.w3.org/2000/svg" shape-rendering="crispEdges" fill="none" stroke="white">
+  <path stroke="black" stroke-width="3.6" stroke-opacity=".75" d="M2,4 l 6,0 l 0,6 l -6,0z M2.5,1.5 l 8,0 l 0,8"/>
+  <rect stroke-width="1.9" x="2" y="4" width="6" height="6"/>
+  <polyline stroke-width=".9" points="3.5,1.5 10.5,1.5 10.5,8.5"/>
+</svg>