[Cleanup] Add missing #include. Remove useless ones.

This CL is the result of running include-what-you-use tool on part
of the code base (audio target and dependencies) plus manual fixes.

bug: webrtc:8311
Change-Id: I277d281ce943c3ecc1bd45fd8d83055931743604
Reviewed-on: https://webrtc-review.googlesource.com/c/106280
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25311}
diff --git a/api/mediaconstraintsinterface.h b/api/mediaconstraintsinterface.h
index 560fa4a..c9a6e1b 100644
--- a/api/mediaconstraintsinterface.h
+++ b/api/mediaconstraintsinterface.h
@@ -21,9 +21,11 @@
 #ifndef API_MEDIACONSTRAINTSINTERFACE_H_
 #define API_MEDIACONSTRAINTSINTERFACE_H_
 
+#include <stddef.h>
 #include <string>
 #include <vector>
 
+#include "api/audio_options.h"
 #include "api/peerconnectioninterface.h"
 
 namespace webrtc {