Bug 1408459, part 1 - Work around compiler problem on Android 4.2 x86 opt. r=erahm,kamidphish

Removing an ununused declaration in nsTraceRefcnt.h causes a compiler
error on Android 4.2 x86 op when CubebUtils.cpp is compiled unified,
for some reason. Work around this by compiling it by itself.

MozReview-Commit-ID: F73D47TU32B

--HG--
extra : rebase_source : 23b76e55e27ab7501f1303a015f67e8be4603283

dom/media/moz.build

@@ -215,7 +215,6 @@ UNIFIED_SOURCES += [
     'ChannelMediaDecoder.cpp',
     'ChannelMediaResource.cpp',
     'CloneableWithRangeMediaResource.cpp',
-    'CubebUtils.cpp',
     'DOMMediaStream.cpp',
     'FileBlockCache.cpp',
     'FileMediaResource.cpp',
@@ -278,8 +277,11 @@ if CONFIG['OS_TARGET'] == 'WINNT':
       'ThreadPoolCOMListener.cpp',
   ]
 
+# CubebUtils.cpp needs to be built separately due to what appears to be some kind
+# of compiler bug on Android 4.2 x86 opt. See bug 1408459.
 # DecoderTraits.cpp needs to be built separately because of Mac OS X headers.
 SOURCES += [
+    'CubebUtils.cpp',
     'DecoderTraits.cpp',
 ]