amstream: Call MediaStreamFilter::SupportSeeking() in AMMultiMediaStream::OpenFile().

dlls/amstream/multimedia.c

@@ -442,6 +442,8 @@ static HRESULT WINAPI multimedia_stream_OpenFile(IAMMultiMediaStream *iface,
     if (SUCCEEDED(ret) && !(flags & AMMSF_NORENDER))
         ret = IGraphBuilder_Render(This->graph, This->ipin);
 
+    IMediaStreamFilter_SupportSeeking(This->filter, This->type == STREAMTYPE_READ);
+
     if (EnumPins)
         IEnumPins_Release(EnumPins);
     if (BaseFilter)

dlls/amstream/tests/amstream.c

@@ -224,9 +224,13 @@ static void test_openfile(void)
     if (pgraph)
         IGraphBuilder_Release(pgraph);
 
+    check_interface(pams, &IID_IMediaSeeking, FALSE);
+
     hr = IAMMultiMediaStream_OpenFile(pams, L"test.avi", 0);
     ok(hr==S_OK, "IAMMultiMediaStream_OpenFile returned: %x\n", hr);
 
+    check_interface(pams, &IID_IMediaSeeking, TRUE);
+
     hr = IAMMultiMediaStream_GetFilterGraph(pams, &pgraph);
     ok(hr==S_OK, "IAMMultiMediaStream_GetFilterGraph returned: %x\n", hr);
     ok(pgraph!=NULL, "Filtergraph should be created\n");