Use WeakPtr in WebRtcEventLogUploaderImpl

This takes care of the case where `url_loader_` posts the callback,
then Cancel() is called before the callback's task was executed,
deleting the object. Following this CL, since now a WeakPtr is used,
that task will just be nullified.

Bug: 1092071
Change-Id: If93c9f9ebef272a648d5eaf9578c5f060de48263
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2260614
Commit-Queue: Elad Alon <eladalon@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781933}

chrome/browser/media/webrtc/webrtc_event_log_uploader.cc

@@ -298,12 +298,10 @@ void WebRtcEventLogUploaderImpl::StartUpload(const std::string& upload_data) {
   url_loader_->SetOnUploadProgressCallback(
       base::BindRepeating(OnURLLoadUploadProgress));
 
-  // See comment in destructor for an explanation about why using
-  // base::Unretained(this) is safe here.
   url_loader_->DownloadToString(
       url_loader_factory_remote.get(),
       base::BindOnce(&WebRtcEventLogUploaderImpl::OnURLLoadComplete,
-                     base::Unretained(this)),
+                     weak_ptr_factory_.GetWeakPtr()),
       kWebRtcEventLogMaxUploadIdBytes);
 }
 

chrome/browser/media/webrtc/webrtc_event_log_uploader.h

@@ -147,6 +147,9 @@ class WebRtcEventLogUploaderImpl : public WebRtcEventLogUploader {
 
   // This object is in charge of the actual upload.
   std::unique_ptr<network::SimpleURLLoader> url_loader_;
+
+  // Allows releasing `this` while a task from `url_loader_` is still pending.
+  base::WeakPtrFactory<WebRtcEventLogUploaderImpl> weak_ptr_factory_{this};
 };
 
 }  // namespace webrtc_event_logging