Move monotonic clock logic out of MediaPipelineBackendForMixer.

Currently there are two nearly-identical declarations/definitions of
MonotonicClockNow: one in MediaPipelineBackendForMixer, and one in
internal chromecast code. With this change, we can use the same function
for both use cases to avoid repeated code.

Test: cast_audio_backend_unittests pass
Bug: b/139928913
Change-Id: Ibe2216b92a0a8f6529297c7ffe35220cad871046
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1771053Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Antonio Rivera <antoniori@google.com>
Auto-Submit: Antonio Rivera <antoniori@google.com>
Cr-Commit-Position: refs/heads/master@{#690830}

chromecast/media/base/BUILD.gn

@@ -2,9 +2,16 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
 import("//chromecast/chromecast.gni")
 import("//third_party/widevine/cdm/widevine.gni")
 
+buildflag_header("buildflags") {
+  header = "buildflags.h"
+
+  flags = [ "MEDIA_CLOCK_MONOTONIC_RAW=$media_clock_monotonic_raw" ]
+}
+
 cast_source_set("key_systems") {
   sources = [
     "key_systems_common.cc",
@@ -109,3 +116,14 @@ cast_source_set("video_plane_controller") {
     "//ui/gfx/geometry",
   ]
 }
+
+cast_source_set("monotonic_clock") {
+  sources = [
+    "monotonic_clock.cc",
+    "monotonic_clock.h",
+  ]
+  deps = [
+    ":buildflags",
+    "//base",
+  ]
+}

chromecast/media/base/monotonic_clock.cc

+// Copyright 2019 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/media/base/monotonic_clock.h"
+
+#include <time.h>
+
+#include "base/time/time.h"
+#include "build/build_config.h"
+
+#if defined(OS_ANDROID) || defined(OS_LINUX)
+#include "chromecast/media/base/buildflags.h"
+#endif  // defined(OS_ANDROID) || defined(OS_LINUX)
+
+#if defined(OS_FUCHSIA)
+#include <zircon/syscalls.h>
+#endif  // defined(OS_FUCHSIA)
+
+namespace chromecast {
+namespace media {
+
+#if defined(OS_ANDROID) || defined(OS_LINUX)
+int64_t MonotonicClockNow() {
+  timespec now = {0, 0};
+#if BUILDFLAG(MEDIA_CLOCK_MONOTONIC_RAW)
+  clock_gettime(CLOCK_MONOTONIC_RAW, &now);
+#else
+  clock_gettime(CLOCK_MONOTONIC, &now);
+#endif  // MEDIA_CLOCK_MONOTONIC_RAW
+  return base::TimeDelta::FromTimeSpec(now).InMicroseconds();
+}
+
+#elif defined(OS_FUCHSIA)
+int64_t MonotonicClockNow() {
+  return zx_clock_get_monotonic() / 1000;
+}
+
+#endif
+
+DefaultMonotonicClock::DefaultMonotonicClock() = default;
+
+DefaultMonotonicClock::~DefaultMonotonicClock() = default;
+
+int64_t DefaultMonotonicClock::Now() {
+  return MonotonicClockNow();
+}
+
+}  // namespace media
+}  // namespace chromecast

chromecast/media/base/monotonic_clock.h

+// Copyright 2019 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_MEDIA_BASE_MONOTONIC_CLOCK_H_
+#define CHROMECAST_MEDIA_BASE_MONOTONIC_CLOCK_H_
+
+#include <stdint.h>
+
+namespace chromecast {
+namespace media {
+
+// Returns the monotonic time (from CLOCK_MONOTONIC) in microseconds.
+// Why not use base::TimeTicks? Because we explicitly need time from
+// CLOCK_MONOTONIC to match the timestamps from CMA GetRenderingDelay(), and
+// base::TimeTicks has no guarantees about which clock it uses (and it could
+// change whenever they feel like it upstream).
+int64_t MonotonicClockNow();
+
+// Interface that provides the monotonic time.
+class MonotonicClock {
+ public:
+  virtual ~MonotonicClock() = default;
+  // Returns the monotonic time in microseconds.
+  virtual int64_t Now() = 0;
+};
+
+// Default implementation of MonotonicClock that uses MonotonicClockNow().
+class DefaultMonotonicClock : public MonotonicClock {
+ public:
+  DefaultMonotonicClock();
+  ~DefaultMonotonicClock() override;
+
+  // MonotonicClock implementation:
+  int64_t Now() override;
+};
+
+}  // namespace media
+}  // namespace chromecast
+
+#endif  // CHROMECAST_MEDIA_BASE_MONOTONIC_CLOCK_H_

chromecast/media/cma/backend/BUILD.gn

@@ -297,6 +297,7 @@ cast_source_set("for_mixer_audio") {
     "//chromecast/base:thread_health_checker",
     "//chromecast/media/audio:libcast_external_audio_pipeline_1.0",
     "//chromecast/media/base",
+    "//chromecast/media/base:monotonic_clock",
     "//chromecast/media/cma/base",
     "//chromecast/media/cma/decoder",
     "//chromecast/public",

chromecast/media/cma/backend/media_pipeline_backend_for_mixer.cc

@@ -5,25 +5,18 @@
 #include "chromecast/media/cma/backend/media_pipeline_backend_for_mixer.h"
 
 #include <time.h>
+
 #include <limits>
 
 #include "base/bind.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
-#include "build/build_config.h"
 #include "chromecast/base/task_runner_impl.h"
+#include "chromecast/media/base/monotonic_clock.h"
 #include "chromecast/media/cma/backend/audio_decoder_for_mixer.h"
 #include "chromecast/media/cma/backend/av_sync.h"
 #include "chromecast/media/cma/backend/video_decoder_for_mixer.h"
 
-#if defined(OS_LINUX)
-#include "chromecast/media/cma/backend/audio_buildflags.h"
-#endif  // defined(OS_LINUX)
-
-#if defined(OS_FUCHSIA)
-#include <zircon/syscalls.h>
-#endif  // defined(OS_FUCHSIA)
-
 namespace {
 
 // Delay video playback to achieve AV sync when video starts.
@@ -239,21 +232,9 @@ MediaPipelineBackendForMixer::GetTaskRunner() const {
   return static_cast<TaskRunnerImpl*>(params_.task_runner)->runner();
 }
 
-#if defined(OS_LINUX)
-int64_t MediaPipelineBackendForMixer::MonotonicClockNow() const {
-  timespec now = {0, 0};
-#if BUILDFLAG(MEDIA_CLOCK_MONOTONIC_RAW)
-  clock_gettime(CLOCK_MONOTONIC_RAW, &now);
-#else
-  clock_gettime(CLOCK_MONOTONIC, &now);
-#endif // MEDIA_CLOCK_MONOTONIC_RAW
-  return base::TimeDelta::FromTimeSpec(now).InMicroseconds();
-}
-#elif defined(OS_FUCHSIA)
 int64_t MediaPipelineBackendForMixer::MonotonicClockNow() const {
-  return zx_clock_get_monotonic() / 1000;
+  return media::MonotonicClockNow();
 }
-#endif
 
 bool MediaPipelineBackendForMixer::IsIgnorePtsMode() const {
   return params_.sync_type ==