[GStreamer] Avoid crash for unexisting pad in webkitGstTraceProcessingTimeForElement

https://bugs.webkit.org/show_bug.cgi?id=258986

Reviewed by Philippe Normand.

In some platforms srcPad can become null, hence crashing. Now it's protected.
We also avoid the cause of the crash in the first place.

* Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::configureElement):
* Source/WebCore/platform/graphics/gstreamer/VideoFrameMetadataGStreamer.cpp:
(webkitGstTraceProcessingTimeForElement):

Canonical link: https://commits.webkit.org/265902@main

Author: calvaris

Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp

@@ -2246,7 +2246,7 @@ void MediaPlayerPrivateGStreamer::configureElement(GstElement* element)
         g_object_set(element, "use-buffering", FALSE, nullptr);
 
     // Collect processing time metrics for video decoders and converters.
-    if ((classifiers.contains("Converter"_s) || classifiers.contains("Decoder"_s)) && classifiers.contains("Video"_s) && !classifiers.contains("Parser"_s))
+    if ((classifiers.contains("Converter"_s) || classifiers.contains("Decoder"_s)) && classifiers.contains("Video"_s) && !classifiers.contains("Parser"_s) && !classifiers.contains("Sink"_s))
         webkitGstTraceProcessingTimeForElement(element);
 
     if (classifiers.contains("Decoder"_s) && classifiers.contains("Video"_s)) {

Source/WebCore/platform/graphics/gstreamer/VideoFrameMetadataGStreamer.cpp

@@ -116,18 +116,25 @@ void webkitGstTraceProcessingTimeForElement(GstElement* element)
         GST_DEBUG_CATEGORY_INIT(webkit_video_frame_meta_debug, "webkitvideoframemeta", 0, "Video frame processing metrics");
     });
 
+    auto sinkPad = adoptGRef(gst_element_get_static_pad(element, "sink"));
+    auto srcPad = adoptGRef(gst_element_get_static_pad(element, "src"));
+    if (!sinkPad || !srcPad) {
+        GST_WARNING("Can't add the processing time probes for %s", GST_OBJECT_NAME(element));
+        ASSERT_NOT_REACHED();
+        return;
+    }
+
     GST_DEBUG("Tracing processing time for %" GST_PTR_FORMAT, element);
-    auto probeType = static_cast<GstPadProbeType>(GST_PAD_PROBE_TYPE_PUSH | GST_PAD_PROBE_TYPE_BUFFER);
 
-    auto sinkPad = adoptGRef(gst_element_get_static_pad(element, "sink"));
+    static auto probeType = static_cast<GstPadProbeType>(GST_PAD_PROBE_TYPE_PUSH | GST_PAD_PROBE_TYPE_BUFFER);
+
     gst_pad_add_probe(sinkPad.get(), probeType, [](GstPad*, GstPadProbeInfo* info, gpointer userData) -> GstPadProbeReturn {
         auto [modifiedBuffer, meta] = ensureVideoFrameMetadata(GST_PAD_PROBE_INFO_BUFFER(info));
         GST_PAD_PROBE_INFO_DATA(info) = modifiedBuffer;
         meta->priv->processingTimes.set(String::fromLatin1(reinterpret_cast<char*>(userData)), std::make_pair(gst_util_get_timestamp(), GST_CLOCK_TIME_NONE));
         return GST_PAD_PROBE_OK;
     }, gst_element_get_name(element), g_free);
 
-    auto srcPad = adoptGRef(gst_element_get_static_pad(element, "src"));
     gst_pad_add_probe(srcPad.get(), probeType, [](GstPad*, GstPadProbeInfo* info, gpointer userData) -> GstPadProbeReturn {
         auto* meta = getInternalVideoFrameMetadata(GST_PAD_PROBE_INFO_BUFFER(info));
         // Some decoders (such as theoradec) do not always copy the input meta to the output frame,