Prevent browser crashes when a site is added to shelf with extensions blacklisted.

chrome/browser/extensions/bookmark_app_helper.cc

Index: chrome/browser/extensions/bookmark_app_helper.cc
diff --git a/chrome/browser/extensions/bookmark_app_helper.cc b/chrome/browser/extensions/bookmark_app_helper.cc
index 5b1e5ef60ee82745bf5542ce8e0244a4d75f41ff..79b63652cc27f0dd61a55dda9587181c3f092f01 100644
--- a/chrome/browser/extensions/bookmark_app_helper.cc
+++ b/chrome/browser/extensions/bookmark_app_helper.cc
@@ -731,14 +731,20 @@ void BookmarkAppHelper::FinishInstallation(const Extension* extension) {
 void BookmarkAppHelper::Observe(int type,
                                 const content::NotificationSource& source,
                                 const content::NotificationDetails& details) {
+  // TODO(dominickn): bookmark app creation fails when extensions cannot be
+  // created (e.g. due to management policies). Add to shelf visibility should
+  // be gated on whether extensions can be created - see crbug.com/545541.
   switch (type) {
     case extensions::NOTIFICATION_CRX_INSTALLER_DONE: {
       const Extension* extension =
           content::Details<const Extension>(details).ptr();
-      DCHECK(extension);
-      DCHECK_EQ(AppLaunchInfo::GetLaunchWebURL(extension),
-                web_app_info_.app_url);
-      FinishInstallation(extension);
+      if (extension) {
+        DCHECK_EQ(AppLaunchInfo::GetLaunchWebURL(extension),
+                  web_app_info_.app_url);
+        FinishInstallation(extension);
+      } else {
+        callback_.Run(nullptr, web_app_info_);
+      }
       break;
     }
     case extensions::NOTIFICATION_EXTENSION_INSTALL_ERROR: