WebUI: add functional test for text_defaults.css

chrome/test/base/web_ui_browser_test.cc

Index: chrome/test/base/web_ui_browser_test.cc
diff --git a/chrome/test/base/web_ui_browser_test.cc b/chrome/test/base/web_ui_browser_test.cc
index d3498f14ed6bbea0540580abc8056fe153a3b480..a356b9f365a0e5c7279d8881f94c5d813342f08a 100644
--- a/chrome/test/base/web_ui_browser_test.cc
+++ b/chrome/test/base/web_ui_browser_test.cc
@@ -32,6 +32,7 @@
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_ui_controller.h"
 #include "content/public/browser/web_ui_message_handler.h"
+#include "content/public/common/url_constants.h"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/test_navigation_observer.h"
 #include "net/base/filename_util.h"
@@ -384,6 +385,8 @@ void WebUIBrowserTest::SetUpOnMainThread() {
 
   test_factory_->AddFactoryOverride(GURL(kDummyURL).host(),
                                     mock_provider_.Pointer());
+  test_factory_->AddFactoryOverride(content::kChromeUIResourcesHost,
+                                    mock_provider_.Pointer());
 }
 
 void WebUIBrowserTest::TearDownOnMainThread() {