Update to Chromium version 88.0.4324.0 (#827102)

- Mac: Xcode 12.2 and the MacOS 11.0 SDK are now required for building.
- MacOS 10.10 (Yosemite) is no longer supported (see https://crbug.com/1126056).
- Flash is no longer supported (see https://www.chromium.org/flash-roadmap).

libcef/browser/audio_loopback_stream_creator.h

@@ -0,0 +1,51 @@
+// Copyright 2018 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 CEF_LIBCEF_BROWSER_AUDIO_LOOPBACK_STREAM_CREATOR_H_
+#define CEF_LIBCEF_BROWSER_AUDIO_LOOPBACK_STREAM_CREATOR_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "content/browser/media/forwarding_audio_stream_factory.h"
+#include "content/common/content_export.h"
+#include "media/mojo/mojom/audio_data_pipe.mojom.h"
+#include "media/mojo/mojom/audio_input_stream.mojom.h"
+#include "mojo/public/cpp/bindings/pending_remote.h"
+
+namespace media {
+class AudioParameters;
+}
+
+// This class handles creating a loopback stream that either captures audio from
+// a WebContents or the system-wide loopback through the Audio Service.
+// This class is operated on the UI thread.
+// Based on InProcessAudioLoopbackStreamCreator which was deleted in
+// https://crrev.com/a5af2468cf.
+class CefAudioLoopbackStreamCreator final {
+ public:
+  CefAudioLoopbackStreamCreator();
+  ~CefAudioLoopbackStreamCreator();
+
+  // The callback that is called when the requested stream is created.
+  using StreamCreatedCallback = base::RepeatingCallback<void(
+      mojo::PendingRemote<media::mojom::AudioInputStream> stream,
+      mojo::PendingReceiver<media::mojom::AudioInputStreamClient>
+          client_receiver,
+      media::mojom::ReadOnlyAudioDataPipePtr data_pipe)>;
+
+  // Creates a loopback stream that captures the audio from |loopback_source|,
+  // or the default system playback if |loopback_source| is null. Local output
+  // of the source/system audio is muted during capturing.
+  void CreateLoopbackStream(content::WebContents* loopback_source,
+                            const media::AudioParameters& params,
+                            uint32_t total_segments,
+                            const StreamCreatedCallback& callback);
+
+ private:
+  content::ForwardingAudioStreamFactory factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(CefAudioLoopbackStreamCreator);
+};
+
+#endif  // CEF_LIBCEF_BROWSER_AUDIO_LOOPBACK_STREAM_CREATOR_H_