[FileSystem]: Use WeakPtr in FileWriterImpl where appropriate.

Bug: 922677
Change-Id: Icd9466fb40cc54e94ffc612801bd73f2e59338ca
Reviewed-on: https://chromium-review.googlesource.com/c/1416630
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623524}

storage/browser/fileapi/file_writer_impl.cc

@@ -17,7 +17,8 @@ FileWriterImpl::FileWriterImpl(
     base::WeakPtr<BlobStorageContext> blob_context)
     : operation_runner_(std::move(operation_runner)),
       blob_context_(std::move(blob_context)),
-      url_(std::move(url)) {
+      url_(std::move(url)),
+      weak_ptr_factory_(this) {
   DCHECK(url_.is_valid());
 }
 
@@ -28,7 +29,7 @@ void FileWriterImpl::Write(uint64_t position,
                            WriteCallback callback) {
   blob_context_->GetBlobDataFromBlobPtr(
       std::move(blob),
-      base::BindOnce(&FileWriterImpl::DoWrite, base::Unretained(this),
+      base::BindOnce(&FileWriterImpl::DoWrite, weak_ptr_factory_.GetWeakPtr(),
                      std::move(callback), position));
 }
 

storage/browser/fileapi/file_writer_impl.h

@@ -6,6 +6,7 @@
 #define STORAGE_BROWSER_FILEAPI_FILE_WRITER_IMPL_H_
 
 #include "base/component_export.h"
+#include "base/memory/weak_ptr.h"
 #include "storage/browser/fileapi/file_system_operation_runner.h"
 #include "storage/browser/fileapi/file_system_url.h"
 #include "third_party/blink/public/mojom/filesystem/file_writer.mojom.h"
@@ -60,6 +61,8 @@ class COMPONENT_EXPORT(STORAGE_BROWSER) FileWriterImpl
   const std::unique_ptr<FileSystemOperationRunner> operation_runner_;
   const base::WeakPtr<BlobStorageContext> blob_context_;
   const FileSystemURL url_;
+
+  base::WeakPtrFactory<FileWriterImpl> weak_ptr_factory_;
 };
 
 }  // namespace storage