Issue #80 - reinstated unified building for some large chunks of our code.

This should reduce compile complexity saving time and reducing linker stress.

dom/media/moz.build

@@ -183,7 +183,7 @@ EXPORTS.mozilla.dom += [
     'VideoTrackList.h',
 ]
 
-SOURCES += [
+UNIFIED_SOURCES += [
     'AccurateSeekTask.cpp',
     'ADTSDecoder.cpp',
     'ADTSDemuxer.cpp',
@@ -200,7 +200,6 @@ SOURCES += [
     'CanvasCaptureMediaStream.cpp',
     'CubebUtils.cpp',
     'DecoderDoctorDiagnostics.cpp',
-    'DecoderTraits.cpp',
     'DOMMediaStream.cpp',
     'EncodedBufferCache.cpp',
     'FileBlockCache.cpp',
@@ -256,6 +255,11 @@ SOURCES += [
 if CONFIG['OS_TARGET'] == 'WINNT':
   SOURCES += [ 'ThreadPoolCOMListener.cpp' ]
 
+# DecoderTraits.cpp needs to be built separately because of Mac OS X headers.
+SOURCES += [
+    'DecoderTraits.cpp',
+]
+
 # Some codec-related code uses multi-character constants, which GCC and clang
 # warn about. Suppress turning this warning into an error.
 if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']: