diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index 624d5ac..cf702c9 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,18 @@
+2018-04-27  Commit Queue  <commit-queue@webkit.org>
+
+        Unreviewed, rolling out r231089.
+        https://bugs.webkit.org/show_bug.cgi?id=185071
+
+        Broke and made crash some WPE EME tests (Requested by calvaris
+        on #webkit).
+
+        Reverted changeset:
+
+        "[EME][GStreamer] Move the decryptor from AppendPipeline to
+        PlaybackPipeline."
+        https://bugs.webkit.org/show_bug.cgi?id=181855
+        https://trac.webkit.org/changeset/231089
+
 2018-04-27  Yacine Bandou  <yacine.bandou_ext@softathome.com>
 
         [EME][GStreamer] Move the decryptor from AppendPipeline to PlaybackPipeline.
diff --git a/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp b/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp
index 8d1b84e..33a330a 100644
--- a/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp
@@ -299,6 +299,23 @@
     gboolean result = FALSE;
 
     switch (GST_EVENT_TYPE(event)) {
+    case GST_EVENT_PROTECTION: {
+        const char* systemId = nullptr;
+
+        gst_event_parse_protection(event, &systemId, nullptr, nullptr);
+        GST_TRACE_OBJECT(self, "received protection event for %s", systemId);
+
+        if (!g_strcmp0(systemId, klass->protectionSystemId)) {
+            GST_DEBUG_OBJECT(self, "sending protection event to the pipeline");
+            gst_element_post_message(GST_ELEMENT(self),
+                gst_message_new_element(GST_OBJECT(self),
+                    gst_structure_new("drm-key-needed", "event", GST_TYPE_EVENT, event, nullptr)));
+        }
+
+        gst_event_unref(event);
+        result = TRUE;
+        break;
+    }
     case GST_EVENT_CUSTOM_DOWNSTREAM_OOB: {
         if (klass->handleKeyResponse(self, event)) {
             GST_DEBUG_OBJECT(self, "key received");
diff --git a/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.cpp b/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.cpp
index 691f0c8..c2508c7 100644
--- a/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.cpp
@@ -55,6 +55,8 @@
         return "NotStarted";
     case AppendPipeline::AppendState::Ongoing:
         return "Ongoing";
+    case AppendPipeline::AppendState::KeyNegotiation:
+        return "KeyNegotiation";
     case AppendPipeline::AppendState::DataStarve:
         return "DataStarve";
     case AppendPipeline::AppendState::Sampling:
@@ -91,6 +93,13 @@
     appendPipeline->handleApplicationMessage(message);
 }
 
+#if ENABLE(ENCRYPTED_MEDIA)
+static void appendPipelineElementMessageCallback(GstBus*, GstMessage* message, AppendPipeline* appendPipeline)
+{
+    appendPipeline->handleElementMessage(message);
+}
+#endif
+
 static void appendPipelineStateChangeMessageCallback(GstBus*, GstMessage* message, AppendPipeline* appendPipeline)
 {
     appendPipeline->handleStateChangeMessage(message);
@@ -122,6 +131,9 @@
 
     g_signal_connect(m_bus.get(), "sync-message::need-context", G_CALLBACK(appendPipelineNeedContextMessageCallback), this);
     g_signal_connect(m_bus.get(), "message::application", G_CALLBACK(appendPipelineApplicationMessageCallback), this);
+#if ENABLE(ENCRYPTED_MEDIA)
+    g_signal_connect(m_bus.get(), "message::element", G_CALLBACK(appendPipelineElementMessageCallback), this);
+#endif
     g_signal_connect(m_bus.get(), "message::state-changed", G_CALLBACK(appendPipelineStateChangeMessageCallback), this);
 
     // We assign the created instances here instead of adoptRef() because gst_bin_add_many()
@@ -263,6 +275,9 @@
     const gchar* contextType = nullptr;
     gst_message_parse_context_type(message, &contextType);
     GST_TRACE("context type: %s", contextType);
+    if (!g_strcmp0(contextType, "drm-preferred-decryption-system-id")
+        && m_appendState != AppendPipeline::AppendState::KeyNegotiation)
+        setAppendState(AppendPipeline::AppendState::KeyNegotiation);
 
     // MediaPlayerPrivateGStreamerBase will take care of setting up encryption.
     if (m_playerPrivate)
@@ -314,6 +329,25 @@
     ASSERT_NOT_REACHED();
 }
 
+#if ENABLE(ENCRYPTED_MEDIA)
+void AppendPipeline::handleElementMessage(GstMessage* message)
+{
+    ASSERT(WTF::isMainThread());
+
+    const GstStructure* structure = gst_message_get_structure(message);
+    GST_TRACE("%s message from %s", gst_structure_get_name(structure), GST_MESSAGE_SRC_NAME(message));
+    if (m_playerPrivate && gst_structure_has_name(structure, "drm-key-needed")) {
+        if (m_appendState != AppendPipeline::AppendState::KeyNegotiation)
+            setAppendState(AppendPipeline::AppendState::KeyNegotiation);
+
+        GST_DEBUG("sending drm-key-needed message from %s to the player", GST_MESSAGE_SRC_NAME(message));
+        GRefPtr<GstEvent> event;
+        gst_structure_get(structure, "event", GST_TYPE_EVENT, &event.outPtr(), nullptr);
+        m_playerPrivate->handleProtectionEvent(event.get());
+    }
+}
+#endif
+
 void AppendPipeline::handleStateChangeMessage(GstMessage* message)
 {
     ASSERT(WTF::isMainThread());
@@ -339,7 +373,7 @@
         return;
     }
 
-    ASSERT(m_appendState == AppendState::Ongoing || m_appendState == AppendState::Sampling);
+    ASSERT(m_appendState == AppendState::KeyNegotiation || m_appendState == AppendState::Ongoing || m_appendState == AppendState::Sampling);
     ASSERT(!m_appsrcNeedDataReceived);
 
     GST_TRACE("received need-data from appsrc");
@@ -397,7 +431,8 @@
     // NotStarted-->Ongoing-->DataStarve-->NotStarted
     //           |         |            `->Aborting-->NotStarted
     //           |         `->Sampling-···->Sampling-->LastSample-->NotStarted
-    //           |                                               `->Aborting-->NotStarted
+    //           |         |                                     `->Aborting-->NotStarted
+    //           |         `->KeyNegotiation-->Ongoing-->[...]
     //           `->Aborting-->NotStarted
     AppendState oldAppendState = m_appendState;
     AppendState nextAppendState = AppendState::Invalid;
@@ -433,8 +468,19 @@
             break;
         }
         break;
+    case AppendState::KeyNegotiation:
+        switch (newAppendState) {
+        case AppendState::Ongoing:
+        case AppendState::Invalid:
+            ok = true;
+            break;
+        default:
+            break;
+        }
+        break;
     case AppendState::Ongoing:
         switch (newAppendState) {
+        case AppendState::KeyNegotiation:
         case AppendState::Sampling:
         case AppendState::Invalid:
             ok = true;
@@ -536,7 +582,18 @@
 
     m_demuxerSrcPadCaps = adoptGRef(demuxerSrcPadCaps);
     m_streamType = WebCore::MediaSourceStreamTypeGStreamer::Unknown;
-
+#if ENABLE(ENCRYPTED_MEDIA)
+    if (areEncryptedCaps(m_demuxerSrcPadCaps.get())) {
+        // Any previous decryptor should have been removed from the pipeline by disconnectFromAppSinkFromStreamingThread()
+        ASSERT(!m_decryptor);
+        GstStructure* structure = gst_caps_get_structure(m_demuxerSrcPadCaps.get(), 0);
+        m_decryptor = GStreamerEMEUtilities::createDecryptor(gst_structure_get_string(structure, "protection-system"));
+        if (!m_decryptor) {
+            GST_ERROR("decryptor not found for caps: %" GST_PTR_FORMAT, m_demuxerSrcPadCaps.get());
+            return;
+        }
+    }
+#endif
     const char* originalMediaType = capsMediaType(m_demuxerSrcPadCaps.get());
     if (!MediaPlayerPrivateGStreamerMSE::supportsCodec(originalMediaType)) {
             m_presentationSize = WebCore::FloatSize();
@@ -616,6 +673,10 @@
     {
         LockHolder locker(m_newSampleLock);
 
+        // If we were in KeyNegotiation but samples are coming, assume we're already OnGoing
+        if (m_appendState == AppendState::KeyNegotiation)
+            setAppendState(AppendState::Ongoing);
+
         // Ignore samples if we're not expecting them. Refuse processing if we're in Invalid state.
         if (m_appendState != AppendState::Ongoing && m_appendState != AppendState::Sampling) {
             GST_WARNING("Unexpected sample, appendState=%s", dumpAppendState(m_appendState));
@@ -948,10 +1009,28 @@
             currentSrcPad = parserSrcPad;
         }
 
+#if ENABLE(ENCRYPTED_MEDIA)
+        if (m_decryptor) {
+            gst_object_ref(m_decryptor.get());
+            gst_bin_add(GST_BIN(m_pipeline.get()), m_decryptor.get());
+            gst_element_sync_state_with_parent(m_decryptor.get());
+
+            GRefPtr<GstPad> decryptorSinkPad = adoptGRef(gst_element_get_static_pad(m_decryptor.get(), "sink"));
+            GRefPtr<GstPad> decryptorSrcPad = adoptGRef(gst_element_get_static_pad(m_decryptor.get(), "src"));
+
+            gst_pad_link(currentSrcPad.get(), decryptorSinkPad.get());
+            currentSrcPad = decryptorSrcPad;
+        }
+#endif
+
         gst_pad_link(currentSrcPad.get(), appsinkSinkPad.get());
 
         gst_element_sync_state_with_parent(m_appsink.get());
 
+#if ENABLE(ENCRYPTED_MEDIA)
+        if (m_pendingDecryptionStructure)
+            dispatchPendingDecryptionStructure();
+#endif
         gst_element_set_state(m_pipeline.get(), GST_STATE_PAUSED);
         gst_element_sync_state_with_parent(m_appsink.get());
 
@@ -1030,6 +1109,14 @@
 
     GST_DEBUG("Disconnecting appsink");
 
+#if ENABLE(ENCRYPTED_MEDIA)
+    if (m_decryptor) {
+        gst_element_set_state(m_decryptor.get(), GST_STATE_NULL);
+        gst_bin_remove(GST_BIN(m_pipeline.get()), m_decryptor.get());
+        m_decryptor = nullptr;
+    }
+#endif
+
     if (m_parser) {
         gst_element_set_state(m_parser.get(), GST_STATE_NULL);
         gst_bin_remove(GST_BIN(m_pipeline.get()), m_parser.get());
@@ -1039,6 +1126,35 @@
     GST_DEBUG_BIN_TO_DOT_FILE_WITH_TS(GST_BIN(m_pipeline.get()), GST_DEBUG_GRAPH_SHOW_ALL, "pad-removed-after");
 }
 
+#if ENABLE(ENCRYPTED_MEDIA)
+void AppendPipeline::dispatchPendingDecryptionStructure()
+{
+    ASSERT(m_decryptor);
+    ASSERT(m_pendingDecryptionStructure);
+    ASSERT(m_appendState == AppendState::KeyNegotiation);
+    GST_TRACE("dispatching key to append pipeline %p", this);
+
+    // Release the m_pendingDecryptionStructure object since
+    // gst_event_new_custom() takes over ownership of it.
+    gst_element_send_event(m_pipeline.get(), gst_event_new_custom(GST_EVENT_CUSTOM_DOWNSTREAM_OOB, m_pendingDecryptionStructure.release()));
+
+    setAppendState(AppendState::Ongoing);
+}
+
+void AppendPipeline::dispatchDecryptionStructure(GUniquePtr<GstStructure>&& structure)
+{
+    if (m_appendState == AppendState::KeyNegotiation) {
+        GST_TRACE("append pipeline %p in key negotiation", this);
+        m_pendingDecryptionStructure = WTFMove(structure);
+        if (m_decryptor)
+            dispatchPendingDecryptionStructure();
+        else
+            GST_TRACE("no decryptor yet, waiting for it");
+    } else
+        GST_TRACE("append pipeline %p not in key negotiation", this);
+}
+#endif
+
 static void appendPipelineAppsinkCapsChanged(GObject* appsinkPad, GParamSpec*, AppendPipeline* appendPipeline)
 {
     GstStructure* structure = gst_structure_new_empty("appsink-caps-changed");
diff --git a/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.h b/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.h
index 995c129..8330466 100644
--- a/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.h
+++ b/Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.h
@@ -42,7 +42,7 @@
 
 class AppendPipeline : public ThreadSafeRefCounted<AppendPipeline> {
 public:
-    enum class AppendState { Invalid, NotStarted, Ongoing, DataStarve, Sampling, LastSample, Aborting };
+    enum class AppendState { Invalid, NotStarted, Ongoing, KeyNegotiation, DataStarve, Sampling, LastSample, Aborting };
 
     AppendPipeline(Ref<MediaSourceClientGStreamerMSE>, Ref<SourceBufferPrivateGStreamer>, MediaPlayerPrivateGStreamerMSE&);
     virtual ~AppendPipeline();
@@ -50,6 +50,9 @@
     void handleNeedContextSyncMessage(GstMessage*);
     void handleApplicationMessage(GstMessage*);
     void handleStateChangeMessage(GstMessage*);
+#if ENABLE(ENCRYPTED_MEDIA)
+    void handleElementMessage(GstMessage*);
+#endif
 
     gint id();
     AppendState appendState() { return m_appendState; }
@@ -57,6 +60,9 @@
 
     GstFlowReturn handleNewAppsinkSample(GstElement*);
     GstFlowReturn pushNewBuffer(GstBuffer*);
+#if ENABLE(ENCRYPTED_MEDIA)
+    void dispatchDecryptionStructure(GUniquePtr<GstStructure>&&);
+#endif
 
     // Takes ownership of caps.
     void parseDemuxerSrcPadCaps(GstCaps*);
@@ -92,6 +98,9 @@
     void handleAppsrcNeedDataReceived();
     void removeAppsrcDataLeavingProbe();
     void setAppsrcDataLeavingProbe();
+#if ENABLE(ENCRYPTED_MEDIA)
+    void dispatchPendingDecryptionStructure();
+#endif
 
     Ref<MediaSourceClientGStreamerMSE> m_mediaSourceClient;
     Ref<SourceBufferPrivateGStreamer> m_sourceBufferPrivate;
@@ -109,6 +118,9 @@
     GRefPtr<GstElement> m_appsrc;
     GRefPtr<GstElement> m_demux;
     GRefPtr<GstElement> m_parser; // Optional.
+#if ENABLE(ENCRYPTED_MEDIA)
+    GRefPtr<GstElement> m_decryptor;
+#endif
     // The demuxer has one src stream only, so only one appsink is needed and linked to it.
     GRefPtr<GstElement> m_appsink;
 
@@ -143,6 +155,9 @@
     RefPtr<WebCore::TrackPrivateBase> m_track;
 
     GRefPtr<GstBuffer> m_pendingBuffer;
+#if ENABLE(ENCRYPTED_MEDIA)
+    GUniquePtr<GstStructure> m_pendingDecryptionStructure;
+#endif
 };
 
 } // namespace WebCore.
diff --git a/Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp b/Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp
index 0436325..a30811f 100644
--- a/Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp
@@ -955,7 +955,8 @@
         gst_structure_set_value(structure.get(), "key-ids", &keyIDList);
         gst_structure_set_value(structure.get(), "key-values", &keyValueList);
 
-        gst_element_send_event(m_playbackPipeline->pipeline(), gst_event_new_custom(GST_EVENT_CUSTOM_DOWNSTREAM_OOB, gst_structure_copy(structure.get())));
+        for (auto it : m_appendPipelinesMap)
+            it.value->dispatchDecryptionStructure(GUniquePtr<GstStructure>(gst_structure_copy(structure.get())));
     }
 }
 #endif
diff --git a/Source/WebCore/platform/graphics/gstreamer/mse/PlaybackPipeline.cpp b/Source/WebCore/platform/graphics/gstreamer/mse/PlaybackPipeline.cpp
index 2b69971..06d5862 100644
--- a/Source/WebCore/platform/graphics/gstreamer/mse/PlaybackPipeline.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/mse/PlaybackPipeline.cpp
@@ -180,9 +180,7 @@
 
     GUniquePtr<gchar> parserBinName(g_strdup_printf("streamparser%u", padId));
 
-    if (areEncryptedCaps(caps)) {
-        GST_DEBUG("It's encrypted content, parsers are not needed before decrypting the content");
-    } else if (!g_strcmp0(mediaType, "video/x-h264")) {
+    if (!g_strcmp0(mediaType, "video/x-h264")) {
         GRefPtr<GstCaps> filterCaps = adoptGRef(gst_caps_new_simple("video/x-h264", "alignment", G_TYPE_STRING, "au", nullptr));
         GstElement* capsfilter = gst_element_factory_make("capsfilter", nullptr);
         g_object_set(capsfilter, "caps", filterCaps.get(), nullptr);