refactor AudioInputDevice to remove race condition.

content/renderer/media/audio_input_message_filter.cc

Index: content/renderer/media/audio_input_message_filter.cc
===================================================================
--- content/renderer/media/audio_input_message_filter.cc	(revision 95453)
+++ content/renderer/media/audio_input_message_filter.cc	(working copy)
@@ -71,15 +71,17 @@
     base::FileDescriptor socket_descriptor,
 #endif
     uint32 length) {
+#if !defined(OS_WIN)
+  base::SyncSocket::Handle socket_handle = socket_descriptor.fd;
+#endif
   Delegate* delegate = delegates_.Lookup(stream_id);
   if (!delegate) {
     DLOG(WARNING) << "Got audio stream event for a non-existent or removed"
         " audio capturer.";
+    base::SharedMemory::CloseHandle(handle);
+    base::SyncSocket socket(socket_handle);
     return;
   }
-#if !defined(OS_WIN)
-  base::SyncSocket::Handle socket_handle = socket_descriptor.fd;
-#endif
   // Forward message to the stream delegate.
   delegate->OnLowLatencyCreated(handle, socket_handle, length);
 }