Block navigations in extensions via ShouldTransferNavigation (not via OpenURL).

chrome/browser/prerender/prerender_contents.cc

Index: chrome/browser/prerender/prerender_contents.cc
diff --git a/chrome/browser/prerender/prerender_contents.cc b/chrome/browser/prerender/prerender_contents.cc
index ff3f72df2f7843134c4347d0b6e7e7a366720489..cfdce0c38e6e5f440a25ca283c9f951126df7c74 100644
--- a/chrome/browser/prerender/prerender_contents.cc
+++ b/chrome/browser/prerender/prerender_contents.cc
@@ -102,7 +102,7 @@ class PrerenderContents::WebContentsDelegateImpl
     return NULL;
   }
 
-  bool ShouldTransferNavigation() override {
+  bool ShouldTransferNavigation(bool is_main_frame_navigation) override {
     // Cancel the prerender if the navigation attempts to transfer to a
     // different process.  Examples include server redirects to privileged pages
     // or cross-site subframe navigations in --site-per-process.