Bug 1564466 - Make MediaSource not call Preferences::GetBool off-main-thread. r=jya

Preferences::GetBool is not thread-safe, StaticPrefs are.
Also StaticPrefs are nicer anyway.

There's a lot of Preferences:: usage in dom/media which looks suspicious, though
I don't know if all that runs on the main thread.

Differential Revision: https://phabricator.services.mozilla.com/D38097

--HG--
extra : moz-landing-system : lando

dom/media/mediasource/MediaSource.cpp

@@ -18,7 +18,6 @@
 #include "SourceBufferList.h"
 #include "mozilla/ErrorResult.h"
 #include "mozilla/FloatingPoint.h"
-#include "mozilla/Preferences.h"
 #include "mozilla/StaticPrefs.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/HTMLMediaElement.h"
@@ -110,13 +109,13 @@ nsresult MediaSource::IsTypeSupported(const nsAString& aType,
   const MediaMIMEType& mimeType = containerType->Type();
   if (mimeType == MEDIAMIMETYPE("video/mp4") ||
       mimeType == MEDIAMIMETYPE("audio/mp4")) {
-    if (!Preferences::GetBool("media.mediasource.mp4.enabled", false)) {
+    if (!StaticPrefs::media_mediasource_mp4_enabled()) {
       return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
     }
     return NS_OK;
   }
   if (mimeType == MEDIAMIMETYPE("video/webm")) {
-    if (!(Preferences::GetBool("media.mediasource.webm.enabled", false) ||
+    if (!(StaticPrefs::media_mediasource_webm_enabled() ||
           StaticPrefs::media_media_capabilities_enabled() ||
           containerType->ExtendedType().Codecs().Contains(
               NS_LITERAL_STRING("vp8")) ||
@@ -131,8 +130,8 @@ nsresult MediaSource::IsTypeSupported(const nsAString& aType,
     return NS_OK;
   }
   if (mimeType == MEDIAMIMETYPE("audio/webm")) {
-    if (!(Preferences::GetBool("media.mediasource.webm.enabled", false) ||
-          Preferences::GetBool("media.mediasource.webm.audio.enabled", true))) {
+    if (!(StaticPrefs::media_mediasource_webm_enabled() ||
+          StaticPrefs::media_mediasource_webm_audio_enabled())) {
       return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
     }
     return NS_OK;
@@ -430,12 +429,14 @@ bool MediaSource::IsTypeSupported(const GlobalObject& aOwner,
 
 /* static */
 bool MediaSource::Enabled(JSContext* cx, JSObject* aGlobal) {
-  return Preferences::GetBool("media.mediasource.enabled");
+  // FIXME(emilio): Looks like this should just use [Pref="..."] on the IDL.
+  return StaticPrefs::media_mediasource_enabled();
 }
 
 /* static */
 bool MediaSource::ExperimentalEnabled(JSContext* cx, JSObject* aGlobal) {
-  return Preferences::GetBool("media.mediasource.experimental.enabled");
+  // FIXME(emilio): Looks like this should just use [Pref="..."] on the IDL.
+  return StaticPrefs::media_mediasource_experimental_enabled();
 }
 
 void MediaSource::SetLiveSeekableRange(double aStart, double aEnd,

modules/libpref/init/StaticPrefList.h

@@ -5770,6 +5770,50 @@ VARCACHE_PREF(
 )
 #undef PREF_VALUE
 
+// MediaSource
+
+// Whether to enable MediaSource support.
+VARCACHE_PREF(
+  Live,
+  "media.mediasource.enabled",
+   media_mediasource_enabled,
+  RelaxedAtomicBool, true
+)
+
+VARCACHE_PREF(
+  Live,
+  "media.mediasource.mp4.enabled",
+   media_mediasource_mp4_enabled,
+  RelaxedAtomicBool, true
+)
+
+VARCACHE_PREF(
+  Live,
+  "media.mediasource.webm.enabled",
+   media_mediasource_webm_enabled,
+  RelaxedAtomicBool,
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_ANDROID)
+  false
+#else
+  true
+#endif
+)
+
+VARCACHE_PREF(
+  Live,
+  "media.mediasource.webm.audio.enabled",
+   media_mediasource_webm_audio_enabled,
+  RelaxedAtomicBool, true
+)
+
+// Whether to enable MediaSource v2 support.
+VARCACHE_PREF(
+  Live,
+  "media.mediasource.experimental.enabled",
+   media_mediasource_experimental_enabled,
+  RelaxedAtomicBool, false
+)
+
 // VideoSink
 VARCACHE_PREF(
   Live,

modules/libpref/init/all.js

@@ -411,21 +411,6 @@ pref("media.webvtt.pseudo.enabled", true);
 // WebVTT debug logging.
 pref("media.webvtt.debug.logging", false);
 
-// Whether to enable MediaSource support.
-pref("media.mediasource.enabled", true);
-
-pref("media.mediasource.mp4.enabled", true);
-
-#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_ANDROID)
-pref("media.mediasource.webm.enabled", false);
-#else
-pref("media.mediasource.webm.enabled", true);
-#endif
-pref("media.mediasource.webm.audio.enabled", true);
-
-// Whether to enable MediaSource v2 support.
-pref("media.mediasource.experimental.enabled", false);
-
 pref("media.benchmark.vp9.threshold", 150);
 pref("media.benchmark.frames", 300);
 pref("media.benchmark.timeout", 1000);