Issue #80 - De-unify dom/media part 1 (updated reland)

This de-unifies up to and including dom/media/platforms with the exception of
dom/media/platforms/wmf, because that one throws weird errors in the Win
SDK which don't have a clear cause (yet)

dom/media/platforms/wrappers/FuzzingWrapper.cpp

@@ -6,6 +6,8 @@
 
 #include "FuzzingWrapper.h"
 
+#include "mozilla/SharedThreadPool.h"
+
 mozilla::LogModule* GetFuzzingWrapperLog() {
   static mozilla::LazyLogModule log("MediaFuzzingWrapper");
   return log;