[Chromecast] Delay volume change until media pipeline setup

Now Renderer::SetVolume will be called before Initialize, which allows
some renderers to do optimization.

CastRenderer volume change relies on MediaPipelineImpl, which is only
available after Initialize. Thus we have to cache the value and set
volume after MediaPipelineImpl becomes available.

Bug: internal b/161747143
Test: Build
Change-Id: I913a2fa5bab102543561725f47e0b7ea19289aa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2314985Reviewed-by: Sergey Volk <servolk@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791136}

chromecast/media/service/cast_renderer.cc

@@ -285,6 +285,11 @@ void CastRenderer::OnGetMultiroomInfo(
     cast_cdm_context_ = nullptr;
   }
 
+  if (pending_volume_.has_value()) {
+    pipeline_->SetVolume(pending_volume_.value());
+    pending_volume_.reset();
+  }
+
   client_ = client;
 
   if (video_stream && video_mode_switcher_) {
@@ -341,11 +346,13 @@ void CastRenderer::SetLatencyHint(
 
 void CastRenderer::Flush(base::OnceClosure flush_cb) {
   DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(pipeline_);
   pipeline_->Flush(std::move(flush_cb));
 }
 
 void CastRenderer::StartPlayingFrom(base::TimeDelta time) {
   DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(pipeline_);
 
   eos_[STREAM_AUDIO] = !pipeline_->HasAudio();
   eos_[STREAM_VIDEO] = !pipeline_->HasVideo();
@@ -359,11 +366,19 @@ void CastRenderer::SetPlaybackRate(double playback_rate) {
 
 void CastRenderer::SetVolume(float volume) {
   DCHECK(task_runner_->BelongsToCurrentThread());
+  // If pipeline is not initialized, cache the volume and delay the volume set
+  // until media pipeline is setup.
+  if (!pipeline_) {
+    pending_volume_ = volume;
+    return;
+  }
+
   pipeline_->SetVolume(volume);
 }
 
 base::TimeDelta CastRenderer::GetMediaTime() {
   DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(pipeline_);
   return pipeline_->GetMediaTime();
 }
 

chromecast/media/service/cast_renderer.h

@@ -10,6 +10,7 @@
 
 #include "base/memory/weak_ptr.h"
 #include "base/no_destructor.h"
+#include "base/optional.h"
 #include "base/unguessable_token.h"
 #include "chromecast/common/mojom/multiroom.mojom.h"
 #include "chromecast/common/mojom/service_connector.mojom.h"
@@ -141,6 +142,8 @@ class CastRenderer : public ::media::Renderer,
     return *g_overlay_composited_callback;
   }
 
+  base::Optional<float> pending_volume_;
+
   base::WeakPtrFactory<CastRenderer> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(CastRenderer);
 };