(4) Rename files to snake_case: update BUILD.gn, include paths, header guards, and DEPS entries

Mechanically generated by running this command:

tools_webrtc/do-renames.sh update all-renames.txt && git cl format

Then manually updating:

tools_webrtc/sanitizers/tsan_suppressions_webrtc.cc

Bug: webrtc:10159
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I54824cd91dada8fc3ee3d098f971bc319d477833
Reviewed-on: https://webrtc-review.googlesource.com/c/115653
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26226}
diff --git a/api/media_stream_interface.h b/api/media_stream_interface.h
index 6d96766..af89e9d 100644
--- a/api/media_stream_interface.h
+++ b/api/media_stream_interface.h
@@ -14,8 +14,8 @@
 // interfaces must be used only with PeerConnection. PeerConnectionManager
 // interface provides the factory methods to create MediaStream and MediaTracks.
 
-#ifndef API_MEDIASTREAMINTERFACE_H_
-#define API_MEDIASTREAMINTERFACE_H_
+#ifndef API_MEDIA_STREAM_INTERFACE_H_
+#define API_MEDIA_STREAM_INTERFACE_H_
 
 #include <stddef.h>
 
@@ -28,7 +28,7 @@
 #include "api/video/video_sink_interface.h"
 #include "api/video/video_source_interface.h"
 #include "modules/audio_processing/include/audio_processing_statistics.h"
-#include "rtc_base/refcount.h"
+#include "rtc_base/ref_count.h"
 #include "rtc_base/scoped_ref_ptr.h"
 
 namespace webrtc {
@@ -294,4 +294,4 @@
 
 }  // namespace webrtc
 
-#endif  // API_MEDIASTREAMINTERFACE_H_
+#endif  // API_MEDIA_STREAM_INTERFACE_H_