Bug 1324306: [MSE] Bump audio memory threshold to 20MB. r=gerald

MozReview-Commit-ID: LSAv3ujW2TX

--HG--
extra : rebase_source : 649dbc4b9d847c3d734c92408467fe309748682c

dom/media/mediasource/TrackBuffersManager.cpp

@@ -100,7 +100,7 @@ TrackBuffersManager::TrackBuffersManager(MediaSourceDecoder* aParentDecoder,
   , mVideoEvictionThreshold(Preferences::GetUint("media.mediasource.eviction_threshold.video",
                                                  100 * 1024 * 1024))
   , mAudioEvictionThreshold(Preferences::GetUint("media.mediasource.eviction_threshold.audio",
-                                                 12 * 1024 * 1024))
+                                                 20 * 1024 * 1024))
   , mEvictionState(EvictionState::NO_EVICTION_NEEDED)
   , mMonitor("TrackBuffersManager")
 {