Bug 1552081 - part1. Sometimes we should run 'TimeMarchesOn' only when the media element's show poster flag is false. r=jya

In the following situations, we should only run `TimeMarchesOn` when the media element's `show-poster` flag is false.

- add cue : https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on-2
- remove cue : https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on-3
- track mode changes : https://html.spec.whatwg.org/multipage/media.html#text-track-model:time-marches-on
- cue's startTime changes : https://html.spec.whatwg.org/multipage/media.html#text-track-api:time-marches-on
- cue's endTime changes : https://html.spec.whatwg.org/multipage/media.html#text-track-api:time-marches-on-2

Differential Revision: https://phabricator.services.mozilla.com/D31376

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

dom/html/HTMLMediaElement.h

@@ -729,6 +729,8 @@ class HTMLMediaElement : public nsGenericHTMLElement,
   // that we can start AudioContext if it was not allowed to start.
   RefPtr<GenericNonExclusivePromise> GetAllowedToPlayPromise();
 
+  bool GetShowPosterFlag() const { return mShowPoster; }
+
  protected:
   virtual ~HTMLMediaElement();
 

dom/html/TextTrackManager.cpp

@@ -202,7 +202,7 @@ void TextTrackManager::AddCues(TextTrack* aTextTrack) {
     for (uint32_t i = 0; i < cueList->Length(); ++i) {
       mNewCues->AddCue(*cueList->IndexedGetter(i, dummy));
     }
-    TimeMarchesOn();
+    MaybeRunTimeMarchesOn();
   }
 }
 
@@ -226,7 +226,7 @@ void TextTrackManager::RemoveTextTrack(TextTrack* aTextTrack,
     for (uint32_t i = 0; i < removeCueList->Length(); ++i) {
       mNewCues->RemoveCue(*((*removeCueList)[i]));
     }
-    TimeMarchesOn();
+    MaybeRunTimeMarchesOn();
   }
 }
 
@@ -281,7 +281,7 @@ void TextTrackManager::NotifyCueAdded(TextTrackCue& aCue) {
   if (mNewCues) {
     mNewCues->AddCue(aCue);
   }
-  TimeMarchesOn();
+  MaybeRunTimeMarchesOn();
   ReportTelemetryForCue();
 }
 
@@ -290,7 +290,7 @@ void TextTrackManager::NotifyCueRemoved(TextTrackCue& aCue) {
   if (mNewCues) {
     mNewCues->RemoveCue(aCue);
   }
-  TimeMarchesOn();
+  MaybeRunTimeMarchesOn();
   DispatchUpdateCueDisplay();
 }
 
@@ -819,7 +819,7 @@ void TextTrackManager::TimeMarchesOn() {
 void TextTrackManager::NotifyCueUpdated(TextTrackCue* aCue) {
   // TODO: Add/Reorder the cue to mNewCues if we have some optimization?
   WEBVTT_LOG("NotifyCueUpdated, cue=%p", aCue);
-  TimeMarchesOn();
+  MaybeRunTimeMarchesOn();
   // For the case "Texttrack.mode = hidden/showing", if the mode
   // changing between showing and hidden, TimeMarchesOn
   // doesn't render the cue. Call DispatchUpdateCueDisplay() explicitly.
@@ -864,5 +864,18 @@ bool TextTrackManager::IsShutdown() const {
   return (mShutdown || !sParserWrapper);
 }
 
+void TextTrackManager::MaybeRunTimeMarchesOn() {
+  MOZ_ASSERT(mMediaElement);
+  // According to spec, we should check media element's show poster flag before
+  // running `TimeMarchesOn` in following situations, (1) add cue (2) remove cue
+  // (3) cue's start time changes (4) cues's end time changes
+  // https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on
+  // https://html.spec.whatwg.org/multipage/media.html#text-track-api:time-marches-on
+  if (mMediaElement->GetShowPosterFlag()) {
+    return;
+  }
+  TimeMarchesOn();
+}
+
 }  // namespace dom
 }  // namespace mozilla

dom/html/TextTrackManager.h

@@ -155,6 +155,10 @@ class TextTrackManager final : public nsIDOMEventListener {
   // report the usage of cue to Telemetry.
   bool mCueTelemetryReported;
 
+  // This function will check media element's show poster flag to decide whether
+  // we need to run `TimeMarchesOn`.
+  void MaybeRunTimeMarchesOn();
+
   class ShutdownObserverProxy final : public nsIObserver {
     NS_DECL_ISUPPORTS