Directly inline shared WebUI CSS declarations into the security and supervised user interstitials.

ui/base/webui/web_ui_util.h

Index: ui/base/webui/web_ui_util.h
diff --git a/ui/base/webui/web_ui_util.h b/ui/base/webui/web_ui_util.h
index 84e06f3170be5d3e336a932458efc5d5447f4f25..df2bbf8cedad45ba751be0e1cc51aaa80a3bbbe9 100644
--- a/ui/base/webui/web_ui_util.h
+++ b/ui/base/webui/web_ui_util.h
@@ -45,10 +45,19 @@ UI_BASE_EXPORT void ParsePathAndScale(const GURL& url,
                                       std::string* path,
                                       float* scale_factor);
 
-// Helper function to set the font family, size, and text direction into the
-// given dictionary.
-UI_BASE_EXPORT void SetFontAndTextDirection(
-    base::DictionaryValue* localized_strings);
+// Helper function to set the text direction on the given dictionary.
+// Note that while this method will also set attributes for default font size
+// and family, using those in JS templates is deprecated, because it might lead
+// to flicker. Instead, use AppendWebUICSSTextDefaults() below.
+// TODO(bauerb): Remove uses of font-family and font-size in JS templates.
+UI_BASE_EXPORT void SetTextDirection(base::DictionaryValue* localized_strings);
+
+// Get a CSS declaration for common text styles for all of Web UI.
+UI_BASE_EXPORT std::string GetWebUICSSTextDefaults();
+
+// Appends the CSS declaration returned by GetWebUICSSTextDefaults() as an
+// inline stylesheet.
+UI_BASE_EXPORT void AppendWebUICSSTextDefaults(std::string* html);
 
 // Get some common font styles for all of WebUI.
 UI_BASE_EXPORT std::string GetFontFamily();