(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/unityplugin/class_reference_holder.cc b/examples/unityplugin/class_reference_holder.cc
index 0ad96c5..00ca772 100644
--- a/examples/unityplugin/class_reference_holder.cc
+++ b/examples/unityplugin/class_reference_holder.cc
@@ -7,7 +7,7 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-#include "examples/unityplugin/classreferenceholder.h"
+#include "examples/unityplugin/class_reference_holder.h"
 
 #include <utility>
 
diff --git a/examples/unityplugin/class_reference_holder.h b/examples/unityplugin/class_reference_holder.h
index 31d6efc..2b0eba4 100644
--- a/examples/unityplugin/class_reference_holder.h
+++ b/examples/unityplugin/class_reference_holder.h
@@ -13,8 +13,8 @@
 // specific java class into JNI c++ side, so that our c++ code can
 // call those java functions.
 
-#ifndef EXAMPLES_UNITYPLUGIN_CLASSREFERENCEHOLDER_H_
-#define EXAMPLES_UNITYPLUGIN_CLASSREFERENCEHOLDER_H_
+#ifndef EXAMPLES_UNITYPLUGIN_CLASS_REFERENCE_HOLDER_H_
+#define EXAMPLES_UNITYPLUGIN_CLASS_REFERENCE_HOLDER_H_
 
 #include <jni.h>
 #include <map>
@@ -34,4 +34,4 @@
 
 }  // namespace unity_plugin
 
-#endif  // EXAMPLES_UNITYPLUGIN_CLASSREFERENCEHOLDER_H_
+#endif  // EXAMPLES_UNITYPLUGIN_CLASS_REFERENCE_HOLDER_H_
diff --git a/examples/unityplugin/jni_onload.cc b/examples/unityplugin/jni_onload.cc
index ebb5bfa..089e9a2 100644
--- a/examples/unityplugin/jni_onload.cc
+++ b/examples/unityplugin/jni_onload.cc
@@ -12,9 +12,9 @@
 #undef JNIEXPORT
 #define JNIEXPORT __attribute__((visibility("default")))
 
-#include "examples/unityplugin/classreferenceholder.h"
-#include "rtc_base/ssladapter.h"
-#include "sdk/android/src/jni/classreferenceholder.h"
+#include "examples/unityplugin/class_reference_holder.h"
+#include "rtc_base/ssl_adapter.h"
+#include "sdk/android/src/jni/class_reference_holder.h"
 #include "sdk/android/src/jni/jni_helpers.h"
 
 namespace webrtc {
diff --git a/examples/unityplugin/simple_peer_connection.cc b/examples/unityplugin/simple_peer_connection.cc
index e1a2552..0b0a810 100644
--- a/examples/unityplugin/simple_peer_connection.cc
+++ b/examples/unityplugin/simple_peer_connection.cc
@@ -16,22 +16,22 @@
 #include "api/audio_codecs/builtin_audio_decoder_factory.h"
 #include "api/audio_codecs/builtin_audio_encoder_factory.h"
 #include "api/create_peerconnection_factory.h"
-#include "api/videosourceproxy.h"
-#include "media/engine/internaldecoderfactory.h"
-#include "media/engine/internalencoderfactory.h"
-#include "media/engine/multiplexcodecfactory.h"
-#include "media/engine/webrtcvideodecoderfactory.h"
-#include "media/engine/webrtcvideoencoderfactory.h"
+#include "api/video_track_source_proxy.h"
+#include "media/engine/internal_decoder_factory.h"
+#include "media/engine/internal_encoder_factory.h"
+#include "media/engine/multiplex_codec_factory.h"
+#include "media/engine/webrtc_video_decoder_factory.h"
+#include "media/engine/webrtc_video_encoder_factory.h"
 #include "modules/audio_device/include/audio_device.h"
 #include "modules/audio_processing/include/audio_processing.h"
 #include "modules/video_capture/video_capture_factory.h"
-#include "pc/videotracksource.h"
+#include "pc/video_track_source.h"
 #include "test/vcm_capturer.h"
 
 #if defined(WEBRTC_ANDROID)
-#include "examples/unityplugin/classreferenceholder.h"
+#include "examples/unityplugin/class_reference_holder.h"
 #include "modules/utility/include/helpers_android.h"
-#include "sdk/android/src/jni/androidvideotracksource.h"
+#include "sdk/android/src/jni/android_video_track_source.h"
 #include "sdk/android/src/jni/jni_helpers.h"
 #endif
 
diff --git a/examples/unityplugin/simple_peer_connection.h b/examples/unityplugin/simple_peer_connection.h
index e4d8a1b..b99bde9 100644
--- a/examples/unityplugin/simple_peer_connection.h
+++ b/examples/unityplugin/simple_peer_connection.h
@@ -16,9 +16,9 @@
 #include <string>
 #include <vector>
 
-#include "api/datachannelinterface.h"
-#include "api/mediastreaminterface.h"
-#include "api/peerconnectioninterface.h"
+#include "api/data_channel_interface.h"
+#include "api/media_stream_interface.h"
+#include "api/peer_connection_interface.h"
 #include "examples/unityplugin/unity_plugin_apis.h"
 #include "examples/unityplugin/video_observer.h"
 
diff --git a/examples/unityplugin/video_observer.h b/examples/unityplugin/video_observer.h
index 84c03d3..01ccd21 100644
--- a/examples/unityplugin/video_observer.h
+++ b/examples/unityplugin/video_observer.h
@@ -13,7 +13,7 @@
 
 #include <mutex>
 
-#include "api/mediastreaminterface.h"
+#include "api/media_stream_interface.h"
 #include "api/video/video_sink_interface.h"
 #include "examples/unityplugin/unity_plugin_apis.h"