URLLoaderClientImpl stores OnTransferSizeUpdated() properly

This CL fixes URLLoaderClientImpl::NeedsStoringMessage() by taking
|accumulated_transfer_size_diff_during_deferred_| into consideration. I hope
this fix crashes around NotifyResourceTransferSizeUpdated() when
ResourceLoadViaDataPipe is on.

Test: ./third_party/blink/tools/run_web_tests.py -t Debug -f external/wpt/webvtt/parsing/file-parsing/tests/header-regions.html --iteration=100
Bug: 926849, 894819, 927184
Change-Id: If5da458dd9eba29c0b47b458a5a09f90b3646b38
Reviewed-on: https://chromium-review.googlesource.com/c/1454344
Commit-Queue: Makoto Shimazu <[email protected]>
Commit-Queue: Yutaka Hirano <[email protected]>
Auto-Submit: Makoto Shimazu <[email protected]>
Reviewed-by: Yutaka Hirano <[email protected]>
Cr-Commit-Position: refs/heads/master@{#629070}

content/renderer/loader/url_loader_client_impl.cc

@@ -379,15 +379,17 @@ void URLLoaderClientImpl::OnComplete(
 }
 
 bool URLLoaderClientImpl::NeedsStoringMessage() const {
-  return is_deferred_ || deferred_messages_.size() > 0;
+  return is_deferred_ || deferred_messages_.size() > 0 ||
+         accumulated_transfer_size_diff_during_deferred_ > 0;
 }
 
 void URLLoaderClientImpl::StoreAndDispatch(
     std::unique_ptr<DeferredMessage> message) {
   DCHECK(NeedsStoringMessage());
   if (is_deferred_) {
     deferred_messages_.push_back(std::move(message));
-  } else if (deferred_messages_.size() > 0) {
+  } else if (deferred_messages_.size() > 0 ||
+             accumulated_transfer_size_diff_during_deferred_ > 0) {
     deferred_messages_.push_back(std::move(message));
     FlushDeferredMessages();
   } else {