Fix unintended local audio "blips" when using the Mirroring Service.

Fixes a bug where local audio unmutes briefly for a second when the
Mirroring Service switches between mirroring and remoting. This is
accomplished by holding a "Muter" sentinel throughout the whole session
to ensure no accidental audio leakage happens while loopback capture is
closed/re-started.

In my quest to fix the bug, it became clear that the
content::AudioLoopbackStreamCreator does not provide the
granularity-of-control needed for the muting bugfix. Thus, this change
has CastMirroringServiceHost invoke the Audio Service mojo APIs
directly.

Bug: 1111026
Change-Id: I9b3e60814306be2179d46a5daeb4c7e8ccee1bdb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2504636Reviewed-by: Jordan Bayles <jophba@chromium.org>
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824740}

chrome/browser/media/cast_mirroring_service_host.h

@@ -19,14 +19,19 @@
 #include "content/public/browser/media_stream_request.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "extensions/buildflags/buildflags.h"
+#include "mojo/public/cpp/bindings/associated_remote.h"
 #include "mojo/public/cpp/bindings/pending_receiver.h"
 #include "mojo/public/cpp/bindings/pending_remote.h"
 #include "mojo/public/cpp/bindings/receiver.h"
 #include "mojo/public/cpp/bindings/remote.h"
+#include "services/audio/public/mojom/stream_factory.mojom.h"
 #include "ui/gfx/geometry/size.h"
 
+namespace base {
+class UnguessableToken;
+}
+
 namespace content {
-class AudioLoopbackStreamCreator;
 class BrowserContext;
 struct DesktopMediaID;
 class WebContents;
@@ -96,13 +101,23 @@ class CastMirroringServiceHost final : public mojom::MirroringServiceHost,
   void GetNetworkContext(
       mojo::PendingReceiver<network::mojom::NetworkContext> receiver) override;
   void CreateAudioStream(
-      mojo::PendingRemote<mojom::AudioStreamCreatorClient> client,
+      mojo::PendingRemote<mojom::AudioStreamCreatorClient> requestor,
       const media::AudioParameters& params,
       uint32_t total_segments) override;
   void ConnectToRemotingSource(
       mojo::PendingRemote<media::mojom::Remoter> remoter,
       mojo::PendingReceiver<media::mojom::RemotingSource> receiver) override;
 
+  void CreateAudioStreamForTab(
+      mojo::PendingRemote<mojom::AudioStreamCreatorClient> requestor,
+      const media::AudioParameters& params,
+      uint32_t total_segments,
+      const base::UnguessableToken& group_id);
+  void CreateAudioStreamForDesktop(
+      mojo::PendingRemote<mojom::AudioStreamCreatorClient> requestor,
+      const media::AudioParameters& params,
+      uint32_t total_segments);
+
   // content::WebContentsObserver implementation.
   void WebContentsDestroyed() override;
 
@@ -136,8 +151,14 @@ class CastMirroringServiceHost final : public mojom::MirroringServiceHost,
   // any.
   std::unique_ptr<viz::GpuClient, base::OnTaskRunnerDeleter> gpu_client_;
 
-  // Used to create an audio loopback stream through the Audio Service.
-  std::unique_ptr<content::AudioLoopbackStreamCreator> audio_stream_creator_;
+  // Used to create WebContents loopback capture streams, or system-wide desktop
+  // capture streams, from the Audio Service.
+  mojo::Remote<audio::mojom::StreamFactory> audio_stream_factory_;
+
+  // Used to mute local audio from the WebContents being mirrored (in the tab
+  // mirrorng case). See the comments in the implementation of
+  // CreateAudioStream() for further explanation.
+  mojo::AssociatedRemote<audio::mojom::LocalMuter> web_contents_audio_muter_;
 
   // The lifetime of the capture indicator icon on the tabstrip is tied to that
   // of |media_stream_ui_|.