Add CastMediaBlocker and BrowserTest

chromecast/browser/cast_media_blocker.h

+// 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 CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_
+#define CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_
+
+#include "base/macros.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace chromecast {
+namespace shell {
+
+// This class implements a blocking mode for web applications and is used in
+// Chromecast internal code.
+class CastMediaBlocker : public content::WebContentsObserver {
+ public:
+  explicit CastMediaBlocker(content::WebContents* web_contents);

[halliwell, 2016/09/13 23:59:47]

nit, forward-declare WebContents

[derekjchow1, 2016/09/14 00:14:05]

Done.

+  ~CastMediaBlocker() override;
+
+  // Sets if the web contents is allowed to play media or not. If media is
+  // unblocked, previously suspended elements should begin playing again.
+  void BlockMediaLoading(bool blocked);
+
+ protected:
+  bool media_loading_blocked() const { return state_ == BLOCKED; }
+
+  // Blocks or unblocks the render process from loading new media
+  // according to |media_loading_blocked_|.
+  virtual void UpdateMediaBlockedState();
+
+ private:
+  enum BlockState {
+    BLOCKED,     // All media playback should be blocked.
+    UNBLOCKING,  // Media playback should be resumed at next oppurtunity.
+    UNBLOCKED,   // Media playback should not be blocked.
+  };
+
+  // content::WebContentsObserver implementation:
+  void MediaSessionStateChanged(
+      bool is_controllable,
+      bool is_suspended,
+      const base::Optional<content::MediaMetadata>& metadata) override;
+
+  // Whether or not media in the app can be controlled and if media is currently
+  // suspended. These variables cache arguments from MediaSessionStateChanged().
+  bool controllable_;
+  bool suspended_;
+
+  BlockState state_;
+
+  DISALLOW_COPY_AND_ASSIGN(CastMediaBlocker);
+};
+
+}  // namespace shell
+}  // namespace chromecast
+
+#endif  // CHROMECAST_BROWSER_CAST_MEDIA_BLOCKER_H_