Don't refer browser-initiated navigations to web-safe URLs to delegate.

extensions/browser/guest_view/web_view/web_view_guest.cc

Index: extensions/browser/guest_view/web_view/web_view_guest.cc
diff --git a/extensions/browser/guest_view/web_view/web_view_guest.cc b/extensions/browser/guest_view/web_view/web_view_guest.cc
index 1ee9252e392997ae23c48fd33d4073ef38bcbff1..661defb5e4287595e21bea7cfe731d584f39e1c6 100644
--- a/extensions/browser/guest_view/web_view/web_view_guest.cc
+++ b/extensions/browser/guest_view/web_view/web_view_guest.cc
@@ -1213,17 +1213,18 @@ void WebViewGuest::AddNewContents(content::WebContents* source,
 content::WebContents* WebViewGuest::OpenURLFromTab(
     content::WebContents* source,
     const content::OpenURLParams& params) {
-  // There are two use cases to consider from a security perspective:
-  // 1.) Renderer-initiated navigation to chrome:// must always be blocked even
-  //     if the <webview> is in WebUI. This is handled by
-  //     WebViewGuest::LoadURLWithParams. WebViewGuest::NavigateGuest will also
-  //     call LoadURLWithParams. CreateNewGuestWebViewWindow creates a new
-  //     WebViewGuest which will call NavigateGuest in DidInitialize.
-  // 2.) The Language Settings context menu item should always work, both in
-  //     Chrome Apps and WebUI. This is a browser initiated request and so
-  //     we pass it along to the embedder's WebContentsDelegate to get the
-  //     browser to perform the action for the <webview>.
-  if (!params.is_renderer_initiated) {
+  // Most navigations should be handled by WebViewGuest::LoadURLWithParams,
+  // which takes care of blocking chrome:// URLs and other web-unsafe schemes.
+  // (NavigateGuest and CreateNewGuestWebViewWindow also go through
+  // LoadURLWithParams.)
+  //
+  // We make an exception here for context menu items, since the Language
+  // Settings item uses a browser-initiated navigation to a chrome:// URL.
+  // These can be passed to the embedder's WebContentsDelegate so that the
+  // browser performs the action for the <webview>.
+  if (!params.is_renderer_initiated &&
+      !content::ChildProcessSecurityPolicy::GetInstance()->IsWebSafeScheme(
+          params.url.scheme())) {
     if (!owner_web_contents()->GetDelegate())
       return nullptr;
     return owner_web_contents()->GetDelegate()->OpenURLFromTab(