Bug 1190496 - Hoist SharedThreadPool into xpcom. r=froydnj

--HG--
rename : dom/media/SharedThreadPool.cpp => xpcom/threads/SharedThreadPool.cpp
rename : dom/media/SharedThreadPool.h => xpcom/threads/SharedThreadPool.h

dom/media/moz.build

@@ -152,7 +152,6 @@ EXPORTS.mozilla += [
     'AbstractThread.h',
     'MediaManager.h',
     'MozPromise.h',
-    'SharedThreadPool.h',
     'StateMirroring.h',
     'StateWatching.h',
     'TaskDispatcher.h',
@@ -235,7 +234,6 @@ UNIFIED_SOURCES += [
     'MP3Demuxer.cpp',
     'MP3FrameParser.cpp',
     'RtspMediaResource.cpp',
-    'SharedThreadPool.cpp',
     'StreamBuffer.cpp',
     'TaskQueue.cpp',
     'TextTrack.cpp',

xpcom/threads/moz.build

@@ -32,6 +32,7 @@ EXPORTS.mozilla += [
     'HangAnnotations.h',
     'HangMonitor.h',
     'LazyIdleThread.h',
+    'SharedThreadPool.h',
     'SyncRunnable.h',
 ]
 
@@ -48,6 +49,7 @@ UNIFIED_SOURCES += [
     'nsThreadManager.cpp',
     'nsThreadPool.cpp',
     'nsTimerImpl.cpp',
+    'SharedThreadPool.cpp',
     'ThreadStackHelper.cpp',
     'TimerThread.cpp',
 ]