[vr] Close exit prompt when clicking on background

chrome/browser/android/vr_shell/ui_elements/content_backplane.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/android/vr_shell/ui_elements/content_backplane.h"
+
+#include "base/memory/ptr_util.h"
+
+namespace vr_shell {
+
+ContentBackplane::ContentBackplane(const base::Callback<void()>& click_callback)

[cjgrant, 2017/06/06 19:42:13]

Documenting an offline conversation, I think the prompt should have its own
backplane, and it also doesn't need to be a separate class.

[ymalik, 2017/06/06 21:11:58]

Done. We do need a separate class since UiElement alone doesn't have the notion
of a callback.

+    : click_callback_(click_callback) {}
+
+ContentBackplane::~ContentBackplane() = default;
+
+void ContentBackplane::OnButtonUp(const gfx::PointF& position) {
+  // We always run the callback. That is, if the user clicks the controller
+  // button on the backplane and releases it on another element in front of the
+  // backplane, this callback will still be called. Elements are input locked
+  // on button down and it's probably not worth special-casing the backplane.
+  click_callback_.Run();
+}
+
+}  // namespace vr_shell