Revert "BlobUrlLoader: Instrument for bug 882661."

This reverts commit 4ff885a.

Reason for revert: CHECK not reached. The URLLoader to blame was the
WebRequestProxyingURLLoader.

Original change's description:
> BlobUrlLoader: Instrument for bug 882661.
> 
> In bug 882661: one mojo::URLLoader is sending OnStartLoadingResponseBody
> without sending OnReceiveResponse before.
> 
> Add instrumentation to check this never happen with this class.
> 
> Bug: 882661
> Change-Id: Ia9df5debbc03f0a5296c64edbcf6d975806bc021
> Reviewed-on: https://chromium-review.googlesource.com/c/1304435
> Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
> Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#605181}

TBR=kinuko@chromium.org,mek@chromium.org,arthursonzogni@chromium.org

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

Bug: 882661
Change-Id: I16e8a5709f34d6909445c9cb0f674f07702ff594
Reviewed-on: https://chromium-review.googlesource.com/c/1329782
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606897}

storage/browser/blob/blob_url_loader.cc

@@ -133,7 +133,6 @@ void BlobURLLoader::DidReadSideData(net::IOBufferWithSize* data) {
 void BlobURLLoader::DidRead(int num_bytes) {
   if (response_body_consumer_handle_.is_valid()) {
     // Send the data pipe on the first OnReadCompleted call.
-    CHECK(on_receive_response_sent_);
     client_->OnStartLoadingResponseBody(
         std::move(response_body_consumer_handle_));
   }
@@ -166,7 +165,7 @@ void BlobURLLoader::HeadersCompleted(net::HttpStatusCode status_code,
   // TODO(jam): some of this code can be shared with
   // services/network/url_loader.h
   client_->OnReceiveResponse(response);
-  on_receive_response_sent_ = true;
+  sent_headers_ = true;
 
   if (metadata) {
     const uint8_t* data = reinterpret_cast<const uint8_t*>(metadata->data());

storage/browser/blob/blob_url_loader.h

@@ -68,13 +68,11 @@ class STORAGE_EXPORT BlobURLLoader : public storage::MojoBlobReader::Delegate,
   net::HttpByteRange byte_range_;
 
   uint64_t total_size_ = 0;
+  bool sent_headers_ = false;
 
   std::unique_ptr<BlobDataHandle> blob_handle_;
   mojo::ScopedDataPipeConsumerHandle response_body_consumer_handle_;
 
-  // TODO(https://crbug.com/882661): Remove this as soon as the bug is fixed.
-  bool on_receive_response_sent_ = false;
-
   base::WeakPtrFactory<BlobURLLoader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BlobURLLoader);