Update poster code as per https://html.spec.whatwg.org/#show-poster-flag

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index ef4a05ad0d62be0329b56a7988629cce0241fb62..3a10a5bebbc09153eecb4796e618d6f59a3d6165 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -332,7 +332,6 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName, Document& docum
     , m_deferredLoadState(NotDeferred)
     , m_deferredLoadTimer(this, &HTMLMediaElement::deferredLoadTimerFired)
     , m_webLayer(nullptr)
-    , m_displayMode(Unknown)
     , m_cachedTime(std::numeric_limits<double>::quiet_NaN())
     , m_fragmentEndTime(std::numeric_limits<double>::quiet_NaN())
     , m_pendingActionFlags(0)
@@ -727,7 +726,7 @@ void HTMLMediaElement::prepareForLoad()
     m_haveFiredLoadedData = false;
     m_completelyLoaded = false;
     m_havePreparedToPlay = false;
-    m_displayMode = Unknown;
+    setShowPoster(true);
 
     // 1 - Abort any already-running instance of the resource selection algorithm for this element.
     m_loadState = WaitingForSource;
@@ -853,7 +852,7 @@ void HTMLMediaElement::selectMediaResource()
             m_loadState = WaitingForSource;
             setShouldDelayLoadEvent(false);
             m_networkState = NETWORK_EMPTY;
-            updateDisplayState();
+            updateDisplayState(false);
 
             WTF_LOG(Media, "HTMLMediaElement::selectMediaResource(%p), nothing to load", this);
             return;
@@ -944,8 +943,7 @@ void HTMLMediaElement::loadResource(const KURL& url, ContentType& contentType, c
 
     startProgressEventTimer();
 
-    // Reset display mode to force a recalculation of what to show because we are resetting the player.
-    setDisplayMode(Unknown);
+    setShowPoster(true);
 
     setPlayerPreload();
 
@@ -989,7 +987,7 @@ void HTMLMediaElement::loadResource(const KURL& url, ContentType& contentType, c
 
     // If there is no poster to display, allow the media engine to render video frames as soon as
     // they are available.
-    updateDisplayState();
+    updateDisplayState(false);
 
     if (layoutObject())
         layoutObject()->updateFromElement();
@@ -1241,7 +1239,7 @@ void HTMLMediaElement::waitForSourceChange()
     // 6.18 - Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
     setShouldDelayLoadEvent(false);
 
-    updateDisplayState();
+    updateDisplayState(false);
 
     if (layoutObject())
         layoutObject()->updateFromElement();
@@ -1280,7 +1278,7 @@ void HTMLMediaElement::noneSupported()
     // 9 - Abort these steps. Until the load() method is invoked or the src attribute is changed,
     // the element won't attempt to load another resource.
 
-    updateDisplayState();
+    updateDisplayState(false);
 
     if (layoutObject())
         layoutObject()->updateFromElement();
@@ -1366,7 +1364,7 @@ void HTMLMediaElement::mediaLoadingFailed(WebMediaPlayer::NetworkState error)
         && m_loadState == LoadingFromSrcAttr)
         noneSupported();
 
-    updateDisplayState();
+    updateDisplayState(false);
     if (mediaControls())
         mediaControls()->reset();
 }
@@ -1569,7 +1567,7 @@ void HTMLMediaElement::setReadyState(ReadyState state)
     }
 
     if (shouldUpdateDisplayState) {
-        updateDisplayState();
+        updateDisplayState(false);
         if (mediaControls())
             mediaControls()->refreshClosedCaptionsButtonVisibility();
     }
@@ -1711,7 +1709,7 @@ void HTMLMediaElement::finishSeek()
     // 17 - Queue a task to fire a simple event named seeked at the element.
     scheduleEvent(EventTypeNames::seeked);
 
-    setDisplayMode(Video);
+    setShowPoster(false);
 }
 
 HTMLMediaElement::ReadyState HTMLMediaElement::readyState() const
@@ -2846,7 +2844,7 @@ void HTMLMediaElement::repaint()
     if (m_webLayer)
         m_webLayer->invalidate();
 
-    updateDisplayState();
+    updateDisplayState(false);
     if (layoutObject())
         layoutObject()->setShouldDoFullPaintInvalidation();
 }
@@ -2959,7 +2957,7 @@ void HTMLMediaElement::updatePlayState()
         this, boolString(shouldBePlaying), boolString(isPlaying));
 
     if (shouldBePlaying) {
-        setDisplayMode(Video);
+        setShowPoster(false);
         invalidateCachedTime();
 
         if (!isPlaying) {