(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/pc/video_track_source.h b/pc/video_track_source.h
index cedb75b..ad0fe09 100644
--- a/pc/video_track_source.h
+++ b/pc/video_track_source.h
@@ -8,13 +8,13 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef PC_VIDEOTRACKSOURCE_H_
-#define PC_VIDEOTRACKSOURCE_H_
+#ifndef PC_VIDEO_TRACK_SOURCE_H_
+#define PC_VIDEO_TRACK_SOURCE_H_
 
-#include "api/mediastreaminterface.h"
+#include "api/media_stream_interface.h"
 #include "api/notifier.h"
 #include "api/video/video_sink_interface.h"
-#include "media/base/mediachannel.h"
+#include "media/base/media_channel.h"
 #include "rtc_base/system/rtc_export.h"
 #include "rtc_base/thread_checker.h"
 
@@ -52,4 +52,4 @@
 
 }  // namespace webrtc
 
-#endif  //  PC_VIDEOTRACKSOURCE_H_
+#endif  //  PC_VIDEO_TRACK_SOURCE_H_