Revert "Add checks to help debug a crash"

This reverts commit a0af9d91.

got enough crash stack to analyze the crash

Original change's description:
> Add checks to help debug a crash
> 
> BUG=1009839
> 
> Change-Id: I2307fb1e693a963b9e472d73dd01cc944b0e3306
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1929438
> Commit-Queue: Min Qin <qinmin@chromium.org>
> Reviewed-by: Xing Liu <xingliu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#717871}

TBR=qinmin@chromium.org,xingliu@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1009839
Change-Id: I30ce8f7232c5fab9ee03d7ad81eadfc7c9a4c31c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1933449Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718498}

components/download/internal/common/download_file_impl.cc

@@ -136,7 +136,6 @@ void DownloadFileImpl::SourceStream::RegisterCompletionCallback(
 InputStream::StreamState DownloadFileImpl::SourceStream::Read(
     scoped_refptr<net::IOBuffer>* data,
     size_t* length) {
-  CHECK(input_stream_);
   return input_stream_->Read(data, length);
 }
 
@@ -178,8 +177,6 @@ DownloadFileImpl::DownloadFileImpl(
 
 DownloadFileImpl::~DownloadFileImpl() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  if (!use_test_task_runner_ && task_runner_)
-    CHECK(!main_task_runner_->BelongsToCurrentThread());
 
   TRACE_EVENT_NESTABLE_ASYNC_END0("download", "DownloadFileActive",
                                   download_id_);
@@ -251,7 +248,7 @@ void DownloadFileImpl::AddInputStream(std::unique_ptr<InputStream> stream,
     CancelRequest(offset);
     return;
   }
-  CHECK(source_streams_.find(offset) == source_streams_.end());
+  DCHECK(source_streams_.find(offset) == source_streams_.end());
   source_streams_[offset] =
       std::make_unique<SourceStream>(offset, offset, std::move(stream));
   OnSourceStreamAdded(source_streams_[offset].get());
@@ -582,17 +579,6 @@ void DownloadFileImpl::StreamActive(SourceStream* source_stream,
   DownloadInterruptReason reason = DOWNLOAD_INTERRUPT_REASON_NONE;
   base::TimeDelta delta(
       base::TimeDelta::FromMilliseconds(kMaxTimeBlockingFileThreadMs));
-
-  // TODO(qinmin): remove this once crbug.com/1009839 is fixed.
-  bool stream_exists = false;
-  for (auto& stream : source_streams_) {
-    SourceStream* stream_ptr = stream.second.get();
-    if (stream_ptr == source_stream) {
-      stream_exists = true;
-      break;
-    }
-  }
-  CHECK(stream_exists);
   // Take care of any file local activity required.
   do {
     state = source_stream->Read(&incoming_data, &incoming_data_size);
@@ -929,7 +915,6 @@ void DownloadFileImpl::DebugStates() const {
 void DownloadFileImpl::SetTaskRunnerForTesting(
     scoped_refptr<base::SequencedTaskRunner> task_runner) {
   task_runner_ = std::move(task_runner);
-  use_test_task_runner_ = true;
 }
 
 DownloadFileImpl::RenameParameters::RenameParameters(

components/download/internal/common/stream_handle_input_stream.cc

@@ -72,8 +72,6 @@ InputStream::StreamState StreamHandleInputStream::Read(
   if (!handle_watcher_)
     return InputStream::EMPTY;
 
-  CHECK(stream_handle_);
-  CHECK(stream_handle_->stream);
   *length = kBytesToRead;
   *data = base::MakeRefCounted<net::IOBuffer>(kBytesToRead);
   MojoResult mojo_result = stream_handle_->stream->ReadData(

components/download/public/common/download_file_impl.h

@@ -382,9 +382,6 @@ class COMPONENTS_DOWNLOAD_EXPORT DownloadFileImpl : public DownloadFile {
   // TaskRunner this object lives on after initialization.
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 
-  // TODO(qinmin): remove this once crbug.com/1009839 is fixed.
-  bool use_test_task_runner_ = false;
-
 #if defined(OS_ANDROID)
   base::FilePath display_name_;
 #endif  // defined(OS_ANDROID)