Bug 1271491: [GMP] P5. Allow GMPDecoderModule::Init() to be called off the main thread. r=cpearce

MozReview-Commit-ID: FLToT0yNTbX

--HG--
extra : rebase_source : c74ddd61d0160c3551380e5a141013759cfc4ec9

dom/media/platforms/agnostic/gmp/GMPDecoderModule.cpp

@@ -13,6 +13,7 @@
 #include "mozIGeckoMediaPluginService.h"
 #include "nsServiceManagerUtils.h"
 #include "mozilla/StaticMutex.h"
+#include "mozilla/SyncRunnable.h"
 #include "gmp-audio-decode.h"
 #include "gmp-video-decode.h"
 #ifdef XP_WIN
@@ -112,7 +113,6 @@ HasGMPFor(const nsACString& aAPI,
           const nsACString& aCodec,
           const nsACString& aGMP)
 {
-  MOZ_ASSERT(NS_IsMainThread());
 #ifdef XP_WIN
   // gmp-clearkey uses WMF for decoding, so if we're using clearkey we must
   // verify that WMF works before continuing.
@@ -130,6 +130,8 @@ HasGMPFor(const nsACString& aAPI,
     }
   }
 #endif
+  MOZ_ASSERT(NS_IsMainThread(),
+             "HasPluginForAPI must be called on the main thread");
   nsTArray<nsCString> tags;
   tags.AppendElement(aCodec);
   tags.AppendElement(aGMP);
@@ -179,8 +181,13 @@ GMPDecoderModule::UpdateUsableCodecs()
 void
 GMPDecoderModule::Init()
 {
-  MOZ_ASSERT(NS_IsMainThread());
-
+  if (!NS_IsMainThread()) {
+    nsCOMPtr<nsIThread> mainThread = do_GetMainThread();
+    nsCOMPtr<nsIRunnable> runnable =
+      NS_NewRunnableFunction([]() { Init(); });
+    SyncRunnable::DispatchToThread(mainThread, runnable);
+    return;
+  }
   // GMPService::HasPluginForAPI is main thread only, so to implement
   // SupportsMimeType() we build a table of the codecs which each whitelisted
   // GMP has and update it when any GMPs are removed or added at runtime.