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/1304435Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605181}

storage/browser/blob/blob_url_loader.cc

@@ -133,6 +133,7 @@ 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_));
   }
@@ -165,7 +166,7 @@ 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);
-  sent_headers_ = true;
+  on_receive_response_sent_ = true;
 
   if (metadata) {
     const uint8_t* data = reinterpret_cast<const uint8_t*>(metadata->data());

storage/browser/blob/blob_url_loader.h

@@ -68,11 +68,13 @@ 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);