[media] Minor clean up without functional changes

We are working on tool to snapshot media implementation in
  #4056
to allow a media implementation snapshot to run side by side with the
default media implementation on Android TV.

The change in drm_system.cc fixes a link conflict when the snapshot and
the default media implementation both have the operator== defined in
global namespace.

The change in player_write_samples.cc reduces the complexity of parsing
function prototype in the tool.

b/327287075

starboard/android/shared/drm_system.cc

@@ -68,7 +68,7 @@ SbDrmSessionRequestType SbDrmSessionRequestTypeFromMediaDrmKeyRequestType(
 
 // This has to be defined outside the above anonymous namespace to be picked up
 // by the comparison of std::vector<SbDrmKeyId>.
-bool operator==(const SbDrmKeyId& left, const SbDrmKeyId& right) {
+inline bool operator==(const SbDrmKeyId& left, const SbDrmKeyId& right) {
   if (left.identifier_size != right.identifier_size) {
     return false;
   }

starboard/shared/starboard/player/player_write_samples.cc

@@ -19,12 +19,15 @@
 
 #if SB_API_VERSION >= 15
 void SbPlayerWriteSamples(SbPlayer player,
+                          SbMediaType sample_type,
+                          const SbPlayerSampleInfo* sample_infos,
+                          int number_of_sample_infos) {
 #else   // SB_API_VERSION >= 15
 void SbPlayerWriteSample2(SbPlayer player,
-#endif  // SB_API_VERSION >= 15
                           SbMediaType sample_type,
                           const SbPlayerSampleInfo* sample_infos,
                           int number_of_sample_infos) {
+#endif  // SB_API_VERSION >= 15
   if (!SbPlayerIsValid(player)) {
     SB_LOG(WARNING) << "player is invalid.";
     return;