Fix crash in ViewManager: fail gracefully when no ServiceProvider is
sent when connecting to ViewManager.

R=sky@chromium.org, jamesr@chromium.org
BUG=

Review URL: https://codereview.chromium.org/989553002

services/view_manager/view_manager_app.cc

diff --git a/services/view_manager/view_manager_app.cc b/services/view_manager/view_manager_app.cc
index ec55f58..715d1b8 100644
--- a/services/view_manager/view_manager_app.cc
+++ b/services/view_manager/view_manager_app.cc
@@ -45,6 +45,9 @@
   connection->AddService<ViewManagerService>(this);
   connection->AddService<WindowManagerInternalClient>(this);
   connection->ConnectToService(&wm_internal_);
+  // If no ServiceProvider has been sent, refuse the connection.
+  if (!wm_internal_)
+    return false;
   wm_internal_.set_error_handler(this);
 
   scoped_ptr<DefaultDisplayManager> display_manager(new DefaultDisplayManager(