Prepare for deleting implicit conversion from raw pointer to scoped_refptr.

Updates all webrtc code, to have a small followup cl to just add the
"explicit" keyword. Patchset #24 passed all webrtc tests, with explicit.

Bug: webrtc:13464
Change-Id: I39863d3752f73209b531120f66916dc9177bf63a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/242363
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35718}

examples/unityplugin/simple_peer_connection.cc

@@ -61,7 +61,7 @@ class CapturerTrackSource : public webrtc::VideoTrackSource {
     if (!capturer) {
       return nullptr;
     }
-    return new rtc::RefCountedObject<CapturerTrackSource>(std::move(capturer));
+    return rtc::make_ref_counted<CapturerTrackSource>(std::move(capturer));
   }
 
  protected: