ExtensionNavigationThrottle: No platform apps in normal tabs.

extensions/browser/extension_navigation_throttle.cc

Index: extensions/browser/extension_navigation_throttle.cc
diff --git a/extensions/browser/extension_navigation_throttle.cc b/extensions/browser/extension_navigation_throttle.cc
index 8fcc2c66ade7d604939000228e137c7cdf5afc4c..731e76956b92c9f7ba92c10e82fc3b350e56a291 100644
--- a/extensions/browser/extension_navigation_throttle.cc
+++ b/extensions/browser/extension_navigation_throttle.cc
@@ -14,6 +14,7 @@
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/guest_view/web_view/web_view_guest.h"
 #include "extensions/browser/url_request_util.h"
+#include "extensions/browser/view_type_utils.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_set.h"
@@ -108,6 +109,20 @@ ExtensionNavigationThrottle::WillStartOrRedirectRequest() {
         return content::NavigationThrottle::BLOCK_REQUEST;
     }
 
+    // Platform apps should only load in app windows, or guest views; never in
+    // regular tabs. TODO(nick): Further restrict the !guest case below.
+    if (target_extension->is_platform_app() && !guest) {
+      switch (GetViewType(web_contents)) {
+        case VIEW_TYPE_APP_WINDOW:
+        case VIEW_TYPE_BACKGROUND_CONTENTS:
+        case VIEW_TYPE_EXTENSION_BACKGROUND_PAGE:
+        case VIEW_TYPE_PANEL:
+          break;
+        default:
+          return content::NavigationThrottle::CANCEL;
+      }
+    }
+
     return content::NavigationThrottle::PROCEED;
   }