Clear BlobReader in SW browser_tests on the right thread

content/browser/service_worker/service_worker_browsertest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 #include <utility>
@@ skipping 2563 matching lines @@
     ASSERT_NE(storage::BlobReader::Status::NET_ERROR, status);
     if (status == storage::BlobReader::Status::DONE)
       OnBlobReaderCalculateSizeCallback(result, continuation, net::OK);
   }
 
   void OnBlobReaderCalculateSizeCallback(int* result,
                                          const base::Closure& continuation,
                                          int size_result) {
     ASSERT_EQ(net::OK, size_result);
     if (!blob_reader_->has_side_data()) {
+      blob_reader_ = nullptr;
       continuation.Run();
       return;
     }
     const storage::BlobReader::Status status = blob_reader_->ReadSideData(
         base::Bind(&self::OnBlobReaderReadSideDataCallback, this, result,
                    continuation));
     ASSERT_NE(storage::BlobReader::Status::NET_ERROR, status);
     if (status == storage::BlobReader::Status::DONE) {
       OnBlobReaderReadSideDataCallback(result, continuation,
                                        storage::BlobReader::Status::DONE);
     }
   }
 
   void OnBlobReaderReadSideDataCallback(int* result,
                                         const base::Closure& continuation,
                                         storage::BlobReader::Status status) {
     ASSERT_NE(storage::BlobReader::Status::NET_ERROR, status);
     *result = blob_reader_->side_data()->size();
+    blob_reader_ = nullptr;
     continuation.Run();
   }
 
   CacheStorageContextImpl* cache_storage_context_;
   storage::FileSystemContext* file_system_context_;
   const GURL origin_;
   const std::string cache_name_;
   const GURL url_;
   std::unique_ptr<storage::BlobDataHandle> blob_data_handle_;
   std::unique_ptr<storage::BlobReader> blob_reader_;
@@ skipping 324 matching lines @@
   // effect in CanSuspendRenderer().
   shell()->web_contents()->WasHidden();
   EXPECT_TRUE(rph->IsProcessBackgrounded());
 
   // The process which has service worker thread shouldn't be suspended.
   EXPECT_FALSE(memory_coordinator->CanSuspendRenderer(render_process_id));
 }
 #endif
 
 }  // namespace content