Add a debug view to the browser that allows various navigation features to be used.

mash/browser/debug_view.h

Index: mash/browser/debug_view.h
diff --git a/mash/browser/debug_view.h b/mash/browser/debug_view.h
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+// Copyright 2016 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.
+
+#ifndef MASH_BROWSER_DEBUG_VIEW_H_
+#define MASH_BROWSER_DEBUG_VIEW_H_
+
+#include "services/navigation/public/interfaces/view.mojom.h"
+#include "ui/views/controls/button/button.h"
+#include "ui/views/view.h"
+
+namespace views {
+class Label;
+class LabelButton;
+class Textfield;
+}  // namespace views
+
+namespace mash {
+namespace browser {
+
+// A panel that shows some controls for compelling the content area of the
+// browser to do specific things.
+class DebugView : public views::View,
+                  public views::ButtonListener {
+ public:
+  DebugView();
+  ~DebugView() override;
+  DebugView(const DebugView&) = delete;
+  void operator=(const DebugView&) = delete;
+
+  void set_view(navigation::mojom::View* view) { view_ = view; }
+
+  gfx::Size GetPreferredSize() const override;
+
+ private:
+  void OnPaint(gfx::Canvas* canvas) override;
+  void ButtonPressed(views::Button* sender, const ui::Event& event) override;
+
+  navigation::mojom::View* view_ = nullptr;
+
+  views::View* interstitial_container_;
+  views::Label* interstitial_label_;
+  views::LabelButton* interstitial_show_;
+  views::LabelButton* interstitial_hide_;
+  views::Textfield* interstitial_content_;
+};
+
+}  // namespace browser
+}  // namespace mash
+
+#endif  // MASH_BROWSER_DEBUG_VIEW_H_