Bug 1887128 - Guess position state from media elements. r=alwu

Differential Revision: https://phabricator.services.mozilla.com/D204691

dom/html/HTMLMediaElement.cpp

@@ -318,7 +318,7 @@ class HTMLMediaElement::MediaControlKeyListener final
 
   MOZ_INIT_OUTSIDE_CTOR explicit MediaControlKeyListener(
       HTMLMediaElement* aElement)
-      : mElement(aElement) {
+      : mElement(aElement), mElementId(nsID::GenerateUUID()) {
     MOZ_ASSERT(NS_IsMainThread());
     MOZ_ASSERT(aElement);
   }
@@ -411,6 +411,33 @@ class HTMLMediaElement::MediaControlKeyListener final
     }
   }
 
+  void NotifyMediaPositionState() {
+    if (!IsStarted()) {
+      return;
+    }
+
+    MOZ_ASSERT(mControlAgent);
+    auto* owner = Owner();
+    PositionState state(owner->Duration(), owner->PlaybackRate(),
+                        owner->CurrentTime(), TimeStamp::Now());
+    MEDIACONTROL_LOG(
+        "Notify media position state (duration=%f, playbackRate=%f, "
+        "position=%f)",
+        state.mDuration, state.mPlaybackRate,
+        state.mLastReportedPlaybackPosition);
+    mControlAgent->UpdateGuessedPositionState(mOwnerBrowsingContextId,
+                                              mElementId, Some(state));
+  }
+
+  void Shutdown() {
+    StopIfNeeded();
+    if (!mControlAgent) {
+      return;
+    }
+    mControlAgent->UpdateGuessedPositionState(mOwnerBrowsingContextId,
+                                              mElementId, Nothing());
+  }
+
   // This method can be called before the listener starts, which would cache
   // the audible state and update after the listener starts.
   void UpdateMediaAudibleState(bool aIsOwnerAudible) {
@@ -543,6 +570,10 @@ class HTMLMediaElement::MediaControlKeyListener final
     MOZ_ASSERT(mState != aState, "Should not notify same state again!");
     mState = aState;
     mControlAgent->NotifyMediaPlaybackChanged(mOwnerBrowsingContextId, mState);
+
+    if (aState == MediaPlaybackState::ePlayed) {
+      NotifyMediaPositionState();
+    }
   }
 
   void NotifyAudibleStateChanged(MediaAudibleState aState) {
@@ -557,6 +588,7 @@ class HTMLMediaElement::MediaControlKeyListener final
   bool mIsPictureInPictureEnabled = false;
   bool mIsOwnerAudible = false;
   MOZ_INIT_OUTSIDE_CTOR uint64_t mOwnerBrowsingContextId;
+  const nsID mElementId;
 };
 
 class HTMLMediaElement::MediaStreamTrackListener
@@ -2065,7 +2097,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLMediaElement,
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSeekDOMPromise)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSetMediaKeysDOMPromise)
   if (tmp->mMediaControlKeyListener) {
-    tmp->mMediaControlKeyListener->StopIfNeeded();
+    tmp->mMediaControlKeyListener->Shutdown();
   }
   if (tmp->mEventBlocker) {
     tmp->mEventBlocker->Shutdown();
@@ -3384,6 +3416,8 @@ void HTMLMediaElement::Seek(double aTime, SeekTarget::Type aSeekType,
 
   // We changed whether we're seeking so we need to AddRemoveSelfReference.
   AddRemoveSelfReference();
+
+  mMediaControlKeyListener->NotifyMediaPositionState();
 }
 
 double HTMLMediaElement::Duration() const {
@@ -6871,6 +6905,7 @@ void HTMLMediaElement::SetPlaybackRate(double aPlaybackRate, ErrorResult& aRv) {
     mDecoder->SetPlaybackRate(ClampPlaybackRate(mPlaybackRate));
   }
   DispatchAsyncEvent(u"ratechange"_ns);
+  mMediaControlKeyListener->NotifyMediaPositionState();
 }
 
 void HTMLMediaElement::SetPreservesPitch(bool aPreservesPitch) {