MediaCodec: Avoid a string copy

We can take our std::string argument by const reference instead
of copy.

Test: TreeHugger
Change-Id: Ia13bfdeead061816444a498d7bc0c7eba4a68d95
diff --git a/media/codec2/sfplugin/CCodec.cpp b/media/codec2/sfplugin/CCodec.cpp
index b47e546..592ff31 100644
--- a/media/codec2/sfplugin/CCodec.cpp
+++ b/media/codec2/sfplugin/CCodec.cpp
@@ -515,7 +515,7 @@
 }
 
 void AmendOutputFormatWithCodecSpecificData(
-        const uint8_t *data, size_t size, const std::string mediaType,
+        const uint8_t *data, size_t size, const std::string &mediaType,
         const sp<AMessage> &outputFormat) {
     if (mediaType == MIMETYPE_VIDEO_AVC) {
         // Codec specific data should be SPS and PPS in a single buffer,