Re-implement the screensaver to use WebView instead of ExtensionDialogHost.

ash/shell/shell_delegate_impl.cc

Index: ash/shell/shell_delegate_impl.cc
diff --git a/ash/shell/shell_delegate_impl.cc b/ash/shell/shell_delegate_impl.cc
index c2bfdc081c882099a1d08c74baef54d6770c70ad..4805957c9b9584da71612614fc130c81ac603916 100644
--- a/ash/shell/shell_delegate_impl.cc
+++ b/ash/shell/shell_delegate_impl.cc
@@ -75,6 +75,10 @@ void ShellDelegateImpl::OpenCrosh() {
 void ShellDelegateImpl::OpenMobileSetup() {
 }
 
+content::BrowserContext* ShellDelegateImpl::GetCurrentBrowserContext() {
+  return Shell::GetInstance()->browser_context();
+}
+
 ash::AppListViewDelegate* ShellDelegateImpl::CreateAppListViewDelegate() {
   return ash::shell::CreateAppListViewDelegate();
 }