Background download: Use weak pointer for DownloadServiceImpl.

Uses weak pointer in DownloadServiceImpl to fix a potential memory
corruption in |pending_tasks_|.

Bug: 860771
Change-Id: Ib84f4c27aa4d2f1e7560434d41175ecba0a622e5
Reviewed-on: https://chromium-review.googlesource.com/1144464Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576754}

components/download/internal/background_service/download_service_impl.cc

@@ -22,9 +22,11 @@ DownloadServiceImpl::DownloadServiceImpl(std::unique_ptr<Configuration> config,
       logger_(std::move(logger)),
       controller_(std::move(controller)),
       service_config_(config_.get()),
-      startup_completed_(false) {
-  controller_->Initialize(base::Bind(
-      &DownloadServiceImpl::OnControllerInitialized, base::Unretained(this)));
+      startup_completed_(false),
+      weak_ptr_factory_(this) {
+  controller_->Initialize(
+      base::BindRepeating(&DownloadServiceImpl::OnControllerInitialized,
+                          weak_ptr_factory_.GetWeakPtr()));
 }
 
 DownloadServiceImpl::~DownloadServiceImpl() = default;

components/download/internal/background_service/download_service_impl.h

@@ -11,6 +11,7 @@
 
 #include "base/containers/circular_deque.h"
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "components/download/internal/background_service/config.h"
 #include "components/download/internal/background_service/service_config_impl.h"
 #include "components/download/public/background_service/download_service.h"
@@ -60,6 +61,8 @@ class DownloadServiceImpl : public DownloadService {
   std::map<DownloadTaskType, base::OnceClosure> pending_tasks_;
   bool startup_completed_;
 
+  base::WeakPtrFactory<DownloadServiceImpl> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadServiceImpl);
 };