Explicitly disallow copy in PlatformThread

Bug: none
Change-Id: If7a7483f742ef5650b991ad659265a598b91a892
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258400
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Markus Handell <handellm@webrtc.org>
Commit-Queue: Markus Handell <handellm@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36494}
diff --git a/rtc_base/platform_thread.h b/rtc_base/platform_thread.h
index 2c82c02..3ab2761 100644
--- a/rtc_base/platform_thread.h
+++ b/rtc_base/platform_thread.h
@@ -55,6 +55,10 @@
   // removed.
   PlatformThread(PlatformThread&& rhs);
 
+  // Copies won't work since we'd have problems with joinable threads.
+  PlatformThread(const PlatformThread&) = delete;
+  PlatformThread& operator=(const PlatformThread&) = delete;
+
   // Moves `rhs` into this, storing an empty state in `rhs`.
   // TODO(bugs.webrtc.org/12727) Look into if default and move support can be
   // removed.