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

ash/test/test_shell_delegate.cc

Index: ash/test/test_shell_delegate.cc
diff --git a/ash/test/test_shell_delegate.cc b/ash/test/test_shell_delegate.cc
index c957e484a7b07c84e4221fa9aa9e897faab13fa4..0dcd1676eda76f307c0db3c1f616256d2b6cf3d5 100644
--- a/ash/test/test_shell_delegate.cc
+++ b/ash/test/test_shell_delegate.cc
@@ -10,6 +10,7 @@
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/test/test_launcher_delegate.h"
+#include "content/test/test_browser_context.h"
 #include "grit/ui_resources.h"
 #include "ui/aura/window.h"
 
@@ -59,6 +60,10 @@ void TestShellDelegate::OpenCrosh() {
 void TestShellDelegate::OpenMobileSetup() {
 }
 
+content::BrowserContext* TestShellDelegate::GetCurrentBrowserContext() {
+  return new TestBrowserContext();
+}
+
 void TestShellDelegate::ToggleSpokenFeedback() {
 }