Bug 1650996 - P2. Always initialise the RemoteDecoderChild manager thread. r=mjf

This allows to simplify the lifetime management off the RemoteDecoderModule's mManagerThread member.

Differential Revision: https://phabricator.services.mozilla.com/D82502

dom/media/ipc/RemoteDecoderChild.h

@@ -55,7 +55,7 @@ class RemoteDecoderChild : public PRemoteDecoderChild,
   MediaDataDecoder::DecodedData mDecodedData;
 
  private:
-  RefPtr<nsIThread> mThread;
+  const RefPtr<nsIThread> mThread;
 
   MozPromiseHolder<MediaDataDecoder::InitPromise> mInitPromise;
   MozPromiseRequestHolder<PRemoteDecoderChild::InitPromise> mInitPromiseRequest;

dom/media/ipc/RemoteDecoderManagerChild.h

@@ -5,9 +5,9 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #ifndef include_dom_media_ipc_RemoteDecoderManagerChild_h
 #define include_dom_media_ipc_RemoteDecoderManagerChild_h
+#include "GPUVideoImage.h"
 #include "mozilla/PRemoteDecoderManagerChild.h"
 #include "mozilla/layers/VideoBridgeUtils.h"
-#include "GPUVideoImage.h"
 
 namespace mozilla {
 
@@ -51,6 +51,7 @@ class RemoteDecoderManagerChild final
   bool DeallocShmem(mozilla::ipc::Shmem& aShmem) override;
 
   // Main thread only
+  static void InitializeThread();
   static void InitForRDDProcess(
       Endpoint<PRemoteDecoderManagerChild>&& aVideoManager);
   static void InitForGPUProcess(
@@ -80,9 +81,6 @@ class RemoteDecoderManagerChild final
   bool DeallocPRemoteDecoderChild(PRemoteDecoderChild* actor);
 
  private:
-  // Main thread only
-  static void InitializeThread();
-
   explicit RemoteDecoderManagerChild(layers::VideoBridgeSource aSource);
   ~RemoteDecoderManagerChild() = default;
 

dom/media/ipc/RemoteDecoderModule.cpp

@@ -22,6 +22,7 @@
 #include "VideoUtils.h"
 #include "VorbisDecoder.h"
 #include "WAVDecoder.h"
+#include "nsIXULRuntime.h"  // for BrowserTabsRemoteAutostart
 
 namespace mozilla {
 
@@ -32,7 +33,17 @@ using namespace layers;
 StaticMutex RemoteDecoderModule::sLaunchMonitor;
 
 RemoteDecoderModule::RemoteDecoderModule()
-    : mManagerThread(RemoteDecoderManagerChild::GetManagerThread()) {}
+    : mManagerThread(RemoteDecoderManagerChild::GetManagerThread()) {
+  MOZ_DIAGNOSTIC_ASSERT(mManagerThread);
+}
+
+/* static */
+void RemoteDecoderModule::Init() {
+  if (!BrowserTabsRemoteAutostart()) {
+    return;
+  }
+  RemoteDecoderManagerChild::InitializeThread();
+}
 
 bool RemoteDecoderModule::SupportsMimeType(
     const nsACString& aMimeType, DecoderDoctorDiagnostics* aDiagnostics) const {
@@ -67,7 +78,7 @@ bool RemoteDecoderModule::SupportsMimeType(
   return supports;
 }
 
-void RemoteDecoderModule::LaunchRDDProcessIfNeeded() {
+void RemoteDecoderModule::LaunchRDDProcessIfNeeded() const {
   if (!XRE_IsContentProcess()) {
     return;
   }
@@ -88,20 +99,17 @@ void RemoteDecoderModule::LaunchRDDProcessIfNeeded() {
   // LaunchRDDProcess which will launch RDD if necessary, and setup the
   // IPC connections between *this* content process and the RDD process.
   bool needsLaunch = true;
-  if (mManagerThread) {
-    RefPtr<Runnable> task = NS_NewRunnableFunction(
-        "RemoteDecoderModule::LaunchRDDProcessIfNeeded-CheckSend", [&]() {
-          if (RemoteDecoderManagerChild::GetRDDProcessSingleton()) {
-            needsLaunch =
-                !RemoteDecoderManagerChild::GetRDDProcessSingleton()->CanSend();
-          }
-        });
-    SyncRunnable::DispatchToThread(mManagerThread, task);
-  }
+  RefPtr<Runnable> task = NS_NewRunnableFunction(
+      "RemoteDecoderModule::LaunchRDDProcessIfNeeded-CheckSend", [&]() {
+        if (RemoteDecoderManagerChild::GetRDDProcessSingleton()) {
+          needsLaunch =
+              !RemoteDecoderManagerChild::GetRDDProcessSingleton()->CanSend();
+        }
+      });
+  SyncRunnable::DispatchToThread(mManagerThread, task);
 
   if (needsLaunch) {
     ContentChild::GetSingleton()->LaunchRDDProcess();
-    mManagerThread = RemoteDecoderManagerChild::GetManagerThread();
   }
 }
 
@@ -109,10 +117,6 @@ already_AddRefed<MediaDataDecoder> RemoteDecoderModule::CreateAudioDecoder(
     const CreateDecoderParams& aParams) {
   LaunchRDDProcessIfNeeded();
 
-  if (!mManagerThread) {
-    return nullptr;
-  }
-
   // OpusDataDecoder will check this option to provide the same info
   // that IsDefaultPlaybackDeviceMono provides.  We want to avoid calls
   // to IsDefaultPlaybackDeviceMono on RDD because initializing audio
@@ -159,10 +163,6 @@ already_AddRefed<MediaDataDecoder> RemoteDecoderModule::CreateVideoDecoder(
     const CreateDecoderParams& aParams) {
   LaunchRDDProcessIfNeeded();
 
-  if (!mManagerThread) {
-    return nullptr;
-  }
-
   RefPtr<RemoteVideoDecoderChild> child = new RemoteVideoDecoderChild();
   MediaResult result(NS_OK);
   // We can use child as a ref here because this is a sync dispatch. In

dom/media/ipc/RemoteDecoderModule.h

@@ -6,7 +6,6 @@
 #ifndef include_dom_media_ipc_RemoteDecoderModule_h
 #define include_dom_media_ipc_RemoteDecoderModule_h
 #include "PlatformDecoderModule.h"
-
 #include "mozilla/StaticMutex.h"
 
 namespace mozilla {
@@ -17,6 +16,8 @@ namespace mozilla {
 // (RemoteVideoDecoderParent) on the RDD process.
 class RemoteDecoderModule : public PlatformDecoderModule {
  public:
+  static void Init();
+
   RemoteDecoderModule();
 
   bool SupportsMimeType(const nsACString& aMimeType,
@@ -29,10 +30,10 @@ class RemoteDecoderModule : public PlatformDecoderModule {
       const CreateDecoderParams& aParams) override;
 
  protected:
-  void LaunchRDDProcessIfNeeded();
+  void LaunchRDDProcessIfNeeded() const;
 
  private:
-  RefPtr<nsIThread> mManagerThread;
+  const nsCOMPtr<nsISerialEventTarget> mManagerThread;
   static StaticMutex sLaunchMonitor;
 };
 

dom/media/platforms/PDMFactory.cpp

@@ -72,6 +72,7 @@ class PDMFactoryImpl final {
 #ifdef MOZ_FFMPEG
     FFmpegRuntimeLinker::Init();
 #endif
+    RemoteDecoderModule::Init();
   }
 };