Don't allow sending data URLs to WebUI, unless in a ChromeOS BalloonHost.

content/public/browser/web_ui_controller_factory.h

Index: content/public/browser/web_ui_controller_factory.h
diff --git a/content/public/browser/web_ui_controller_factory.h b/content/public/browser/web_ui_controller_factory.h
index 412006efbf0933bc928471c2e9ac4c7e88574545..871bea1eaf003b38250190823050f65b772c9dbc 100644
--- a/content/public/browser/web_ui_controller_factory.h
+++ b/content/public/browser/web_ui_controller_factory.h
@@ -48,7 +48,8 @@ class CONTENT_EXPORT WebUIControllerFactory {
   // URLs with WebUI types (as above) and also URLs that can be loaded by
   // normal tabs such as javascript: URLs or about:hang.
   virtual bool IsURLAcceptableForWebUI(BrowserContext* browser_context,
-                                       const GURL& url) const = 0;
+                                       const GURL& url,
+                                       bool data_urls_allowed) const = 0;
 };
 
 }  // namespace content