Add CastMediaBlocker and BrowserTest

chromecast/browser/cast_media_blocker.cc

Index: chromecast/browser/cast_media_blocker.cc
diff --git a/chromecast/browser/cast_media_blocker.cc b/chromecast/browser/cast_media_blocker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8644c1a1ac1d3b2511f0366e136890b1f578dd86
--- /dev/null
+++ b/chromecast/browser/cast_media_blocker.cc
@@ -0,0 +1,60 @@
+// 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.
+
+#include "chromecast/browser/cast_media_blocker.h"
+
+#include "base/threading/thread_checker.h"
+#include "content/public/browser/web_contents.h"
+
+namespace chromecast {
+namespace shell {
+
+CastMediaBlocker::CastMediaBlocker(content::WebContents* web_contents)
+    : content::WebContentsObserver(web_contents),
+      controllable_(false),
+      suspended_(false),
+      state_(UNBLOCKED) {}
+
+CastMediaBlocker::~CastMediaBlocker() {}
+
+void CastMediaBlocker::BlockMediaLoading(bool blocked) {
+  if (blocked) {
+    state_ = BLOCKED;
+  } else {
+    state_ = (state_ == BLOCKED ? UNBLOCKING : UNBLOCKED);

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

Can state_ be UNBLOCKING when this is called?  If so, why does it transition to
UNBLOCKED here?  I thought the UNBLOCKING->UNBLOCKED transition should only
happen when Resume is called?

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

Good point. If we're unblocking, we should always go to the UNBLOCKING state,
unless we're already UNBLOCKED.

+  }
+
+  UpdateMediaBlockedState();
+}
+
+void CastMediaBlocker::UpdateMediaBlockedState() {
+  if (!web_contents()) {
+    return;
+  }
+
+  if (!controllable_) {
+    return;
+  }
+
+  if (state_ == BLOCKED && !suspended_) {
+    web_contents()->SuspendMediaSession();
+  }
+
+  if (state_ == UNBLOCKING && suspended_) {
+    web_contents()->ResumeMediaSession();
+    state_ = UNBLOCKED;
+  }
+}
+
+void CastMediaBlocker::MediaSessionStateChanged(
+    bool is_controllable,
+    bool is_suspended,
+    const base::Optional<content::MediaMetadata>& metadata) {
+  controllable_ = is_controllable;
+  suspended_ = is_suspended;
+  UpdateMediaBlockedState();
+}
+
+}  // namespace shell
+}  // namespace chromecast