Add UI thread KeyboardMicRegistration implementation.

Used by AudioInputStreamBroker (introduced in dependent CL) instead of
AudioInputDeviceManager::KeyboardMicRegistration implementation, in order to avoid thread jumps and
to keep broker interface simple.

AudioInputDeviceManager::KeyboardMicRegistration will be removed after switching to audio service
input streams.

Bug: 828868
Change-Id: I41aac3e01faeb0d4d47f98726bc069640fb346e3
Reviewed-on: https://chromium-review.googlesource.com/1044216
Commit-Queue: Marina Ciocea <marinaciocea@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556390}

content/browser/BUILD.gn

@@ -1739,6 +1739,8 @@ jumbo_source_set("browser") {
   # ChromeOS also defines linux but their memory-monitors conflict.
   if (is_chromeos) {
     sources += [
+      "media/keyboard_mic_registration.cc",
+      "media/keyboard_mic_registration.h",
       "memory/memory_monitor_chromeos.cc",
       "memory/memory_monitor_chromeos.h",
       "tracing/cros_tracing_agent.cc",

content/browser/browser_main_loop.h

@@ -19,6 +19,10 @@
 #include "services/viz/public/interfaces/compositing/compositing_mode_watcher.mojom.h"
 #include "ui/base/ui_features.h"
 
+#if defined(OS_CHROMEOS)
+#include "content/browser/media/keyboard_mic_registration.h"
+#endif
+
 #if defined(USE_AURA)
 namespace aura {
 class Env;
@@ -166,6 +170,13 @@ class CONTENT_EXPORT BrowserMainLoop {
   media::UserInputMonitor* user_input_monitor() const {
     return user_input_monitor_.get();
   }
+
+#if defined(OS_CHROMEOS)
+  KeyboardMicRegistration* keyboard_mic_registration() {
+    return &keyboard_mic_registration_;
+  }
+#endif
+
   discardable_memory::DiscardableSharedMemoryManager*
   discardable_shared_memory_manager() const {
     return discardable_shared_memory_manager_.get();
@@ -344,6 +355,10 @@ class CONTENT_EXPORT BrowserMainLoop {
   scoped_refptr<base::DeferredSequencedTaskRunner> audio_service_runner_;
   std::unique_ptr<media::AudioSystem> audio_system_;
 
+#if defined(OS_CHROMEOS)
+  KeyboardMicRegistration keyboard_mic_registration_;
+#endif
+
   std::unique_ptr<midi::MidiService> midi_service_;
 
   // Must be deleted on the IO thread.

content/browser/media/keyboard_mic_registration.cc

+// 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.
+
+#include "content/browser/media/keyboard_mic_registration.h"
+
+#include "chromeos/audio/cras_audio_handler.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+KeyboardMicRegistration::KeyboardMicRegistration() = default;
+
+KeyboardMicRegistration::~KeyboardMicRegistration() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK_EQ(0, register_count_);
+}
+
+void KeyboardMicRegistration::Register() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (++register_count_ == 1)
+    chromeos::CrasAudioHandler::Get()->SetKeyboardMicActive(true);
+}
+
+void KeyboardMicRegistration::Deregister() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (--register_count_ == 0)
+    chromeos::CrasAudioHandler::Get()->SetKeyboardMicActive(false);
+}
+
+}  // namespace content

content/browser/media/keyboard_mic_registration.h

+// 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 CONTENT_BROWSER_MEDIA_KEYBOARD_MIC_REGISTRATION_H_
+#define CONTENT_BROWSER_MEDIA_KEYBOARD_MIC_REGISTRATION_H_
+
+#include "base/macros.h"
+
+namespace content {
+
+// Chrome OS keyboard mic stream registration. Used on UI thread only and owned
+// by BrowserMainLoop; instance must be obtained through
+// BrowserMainLoop::keyboard_mic_registration().
+class KeyboardMicRegistration {
+ public:
+  KeyboardMicRegistration();
+  ~KeyboardMicRegistration();
+
+  void Register();
+  void Deregister();
+
+ private:
+  int register_count_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(KeyboardMicRegistration);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_KEYBOARD_MIC_REGISTRATION_H_