Allow content script insertion on about:-URLs.

chrome/test/data/extensions/api_test/content_scripts/about_blank_iframes/content_script2.js

Index: chrome/test/data/extensions/api_test/content_scripts/about_blank_iframes/content_script2.js
diff --git a/ui/native_theme/native_theme_observer.cc b/chrome/test/data/extensions/api_test/content_scripts/about_blank_iframes/content_script2.js
similarity index 55%
copy from ui/native_theme/native_theme_observer.cc
copy to chrome/test/data/extensions/api_test/content_scripts/about_blank_iframes/content_script2.js
index f516a762027fccab32d569f2466d82c65252c104..1900c29ce78ec10b8f5b42290068522fbfc570da 100644
--- a/ui/native_theme/native_theme_observer.cc
+++ b/chrome/test/data/extensions/api_test/content_scripts/about_blank_iframes/content_script2.js
@@ -2,10 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "ui/native_theme/native_theme_observer.h"
-
-namespace ui {
-
-NativeThemeObserver::~NativeThemeObserver() {}
-
-}  // namespace ui
+chrome.extension.sendRequest('This content script should never be executed.');