Cherry-pick 275166@main (764cbc5). https://bugs.webkit.org/show_bug.c…

…gi?id=269838

    [LibWebRTC][GStreamer] Incoming H.264 stream parsing fails
    https://bugs.webkit.org/show_bug.cgi?id=269838

    Reviewed by Xabier Rodriguez-Calvar.

    Workaround cases where the GStreamer LibWebRTC decoder is expected to process frames with invalid
    render time.

    * Source/WebCore/platform/mediastream/libwebrtc/gstreamer/GStreamerVideoDecoderFactory.cpp:
    (WebCore::GStreamerVideoDecoder::GstDecoderFactory):

    Canonical link: https://commits.webkit.org/275166@main

Canonical link: https://commits.webkit.org/274313.178@webkitglib/2.44

Source/WebCore/platform/mediastream/libwebrtc/gstreamer/GStreamerVideoDecoderFactory.cpp

@@ -198,6 +198,14 @@ class GStreamerWebRTCVideoDecoder : public webrtc::VideoDecoder {
             return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
         }
 
+        // No renderTime provided, probably some issue with the WebRTC clock. Use a monotonically
+        // incrementing counter instead.
+        static int64_t s_forgedRenderTime { 0 };
+        if (!renderTimeMs) {
+            renderTimeMs = s_forgedRenderTime;
+            s_forgedRenderTime += 30 * GST_MSECOND;
+        }
+
         if (!GST_CLOCK_TIME_IS_VALID(m_firstBufferPts)) {
             GRefPtr<GstPad> srcpad = adoptGRef(gst_element_get_static_pad(m_src, "src"));
             m_firstBufferPts = (static_cast<guint64>(renderTimeMs)) * GST_MSECOND;
@@ -277,7 +285,7 @@ class GStreamerWebRTCVideoDecoder : public webrtc::VideoDecoder {
         return { webrtc::SdpVideoFormat(Name()) };
     }
 
-    static GRefPtr<GstElementFactory> GstDecoderFactory(const char *capsStr)
+    static GRefPtr<GstElementFactory> GstDecoderFactory(const char* capsStr)
     {
         auto allDecoders = gst_element_factory_list_get_elements(GST_ELEMENT_FACTORY_TYPE_DECODER,
             GST_RANK_MARGINAL);