moved decodercache to base folder for shared usage

app/render/backend/decodercache.cpp

@@ -0,0 +1,21 @@
+#include "decodercache.h"
+
+DecoderCache::DecoderCache()
+{
+
+}
+
+void DecoderCache::Clear()
+{
+  decoders_.clear();
+}
+
+void DecoderCache::AddDecoder(Stream *stream, DecoderPtr shader)
+{
+  decoders_.insert(stream, shader);
+}
+
+DecoderPtr DecoderCache::GetDecoder(Stream *stream)
+{
+  return decoders_.value(stream);
+}