(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/examples/peerconnection/client/main_wnd.h b/examples/peerconnection/client/main_wnd.h
index 5700258..898fea9 100644
--- a/examples/peerconnection/client/main_wnd.h
+++ b/examples/peerconnection/client/main_wnd.h
@@ -15,11 +15,11 @@
 #include <memory>
 #include <string>
 
-#include "api/mediastreaminterface.h"
+#include "api/media_stream_interface.h"
 #include "api/video/video_frame.h"
 #include "examples/peerconnection/client/peer_connection_client.h"
-#include "media/base/mediachannel.h"
-#include "media/base/videocommon.h"
+#include "media/base/media_channel.h"
+#include "media/base/video_common.h"
 #if defined(WEBRTC_WIN)
 #include "rtc_base/win32.h"
 #endif  // WEBRTC_WIN