Bug 1096469 - Make devedition theme work with custom devtools themes;r=Gijs

browser/base/content/browser-devedition.js

@@ -53,8 +53,11 @@ let DevEdition = {
   _updateDevtoolsThemeAttribute: function() {
     // Set an attribute on root element to make it possible
     // to change colors based on the selected devtools theme.
-    document.documentElement.setAttribute("devtoolstheme",
-      Services.prefs.getCharPref(this._devtoolsThemePrefName));
+    let devtoolsTheme = Services.prefs.getCharPref(this._devtoolsThemePrefName);
+    if (devtoolsTheme != "dark") {
+      devtoolsTheme = "light";
+    }
+    document.documentElement.setAttribute("devtoolstheme", devtoolsTheme);
     ToolbarIconColor.inferFromText();
     this._updateStyleSheetFromPrefs();
   },

browser/base/content/test/general/browser_devedition.js

@@ -65,6 +65,11 @@ function testDevtoolsTheme() {
   is (document.documentElement.getAttribute("devtoolstheme"), "dark",
     "The documentElement has an attribute based on devtools theme.");
   ok (DevEdition.styleSheet, "The devedition stylesheet is still there with the dark devtools theme.");
+
+  Services.prefs.setCharPref(PREF_DEVTOOLS_THEME, "foobar");
+  is (document.documentElement.getAttribute("devtoolstheme"), "light",
+    "The documentElement has 'light' as a default for the devtoolstheme attribute");
+  ok (DevEdition.styleSheet, "The devedition stylesheet is still there with the foobar devtools theme.");
 }
 
 function dummyLightweightTheme(id) {