avoid poster flicker during video looping or random seek operation

Source/core/html/HTMLVideoElement.cpp

Index: Source/core/html/HTMLVideoElement.cpp
diff --git a/Source/core/html/HTMLVideoElement.cpp b/Source/core/html/HTMLVideoElement.cpp
index 4399b983af84cec75bae3b7ce0fd9b34920bb424..b9df940c4b45a7e8547b6d2ea528d39773519756 100644
--- a/Source/core/html/HTMLVideoElement.cpp
+++ b/Source/core/html/HTMLVideoElement.cpp
@@ -167,7 +167,9 @@ void HTMLVideoElement::setDisplayMode(DisplayMode mode)
     if (!poster.isEmpty()) {
         // We have a poster path, but only show it until the user triggers display by playing or seeking and the
         // media engine has something to display.
-        if (mode == Video && !hasAvailableVideoFrame())
+        // Don't show the poster if there is a seek operation or
+        // the video has restarted because of loop attribute
+        if (mode == Video && oldMode == Poster && !hasAvailableVideoFrame())
             mode = PosterWaitingForVideo;
     }