diff -up firefox-52.0.2/modules/libpref/init/all.js.1158076-1 firefox-52.0.2/modules/libpref/init/all.js
--- firefox-52.0.2/modules/libpref/init/all.js.1158076-1	2017-03-31 09:44:28.377647329 +0200
+++ firefox-52.0.2/modules/libpref/init/all.js	2017-03-31 09:46:02.847234586 +0200
@@ -4646,6 +4646,8 @@ pref("gfx.apitrace.enabled",false);
 pref("gfx.content.use-native-pushlayer", true);
 #ifdef MOZ_WIDGET_GTK
 pref("gfx.xrender.enabled",false);
+pref("widget.chrome.allow-gtk-dark-theme", false);
+pref("widget.content.allow-gtk-dark-theme", false);
 #endif
 #endif
 
diff -up firefox-52.0.2/widget/gtk/nsLookAndFeel.cpp.1158076-1 firefox-52.0.2/widget/gtk/nsLookAndFeel.cpp
--- firefox-52.0.2/widget/gtk/nsLookAndFeel.cpp.1158076-1	2017-03-31 09:44:28.374647342 +0200
+++ firefox-52.0.2/widget/gtk/nsLookAndFeel.cpp	2017-03-31 09:44:35.125617758 +0200
@@ -1134,16 +1134,27 @@ nsLookAndFeel::Init()
     // with wrong color theme, see Bug 972382
     GtkSettings *settings = gtk_settings_get_for_screen(gdk_screen_get_default());
 
-    // Disable dark theme because it interacts poorly with widget styling in
-    // web content (see bug 1216658).
-    // To avoid triggering reload of theme settings unnecessarily, only set the
-    // setting when necessary.
     const gchar* dark_setting = "gtk-application-prefer-dark-theme";
-    gboolean dark;
-    g_object_get(settings, dark_setting, &dark, nullptr);
+    gboolean darkThemeDefault;
+    g_object_get(settings, dark_setting, &darkThemeDefault, nullptr);
 
-    if (dark && !PR_GetEnv("MOZ_ALLOW_GTK_DARK_THEME")) {
-        g_object_set(settings, dark_setting, FALSE, nullptr);
+    // Dark themes interacts poorly with widget styling (see bug 1216658).
+    // We disable dark themes by default for all processes (chrome, web content)
+    // but allow user to overide it by prefs.
+    if (darkThemeDefault) {
+        bool allowDarkTheme;
+        if (XRE_IsContentProcess()) {
+            allowDarkTheme =
+                mozilla::Preferences::GetBool("widget.content.allow-gtk-dark-theme",
+                                              false);
+        } else {
+            allowDarkTheme = (PR_GetEnv("MOZ_ALLOW_GTK_DARK_THEME") != nullptr) ||
+                mozilla::Preferences::GetBool("widget.chrome.allow-gtk-dark-theme",
+                                              false);
+        }
+        if (!allowDarkTheme) {
+            g_object_set(settings, dark_setting, FALSE, nullptr);
+        }
     }
 
     // Scrollbar colors