ReadableStream: Resolve BYOB reads immediately on cancel

This CL is based on spec changes made in whatwg/streams#1129.

Summary/context of changes:
If you cancel a stream while a BYOB read is pending, the stream
should simply not give back the buffer. This means that cancel()
can immediately resolve all pending BYOB reads with the classic
{ done: true, value: undefined }, without having to wait for the
underlying byte source. Also, when the stream is cancelled, any
pending BYOB request is now immediately invalidated, so the
underlying byte source doesn't erroneously think that it still
needs to provide a response.

Bug: 1223565
Change-Id: I17d1d5cfaee80c02c51bc682447b381ade4363bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3216778
Commit-Queue: Nidhi Jaju <nidhijaju@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/main@{#930987}

third_party/blink/renderer/core/streams/readable_byte_stream_controller.cc

@@ -1442,13 +1442,8 @@ v8::Local<v8::Promise> ReadableByteStreamController::CancelSteps(
     ScriptState* script_state,
     v8::Local<v8::Value> reason) {
   // https://streams.spec.whatwg.org/#rbs-controller-private-cancel
-  // 1. If this.[[pendingPullIntos]] is not empty,
-  if (!pending_pull_intos_.IsEmpty()) {
-    //   a. Let firstDescriptor be this.[[pendingPullIntos]][0].
-    PullIntoDescriptor* first_descriptor = pending_pull_intos_[0];
-    //   b. Set firstDescriptor’s bytes filled to 0.
-    first_descriptor->bytes_filled = 0;
-  }
+  // 1. Perform ! ReadableByteStreamControllerClearPendingPullIntos(this).
+  ClearPendingPullIntos(this);
   // 2. Perform ! ResetQueue(this).
   ResetQueue(this);
   // 3. Let result be the result of performing this.[[cancelAlgorithm]], passing

third_party/blink/renderer/core/streams/readable_stream.cc

@@ -1732,7 +1732,25 @@ v8::Local<v8::Promise> ReadableStream::Cancel(ScriptState* script_state,
   // 4. Perform ! ReadableStreamClose(stream).
   Close(script_state, stream);
 
-  // 5. Let sourceCancelPromise be ! stream.[[readableStreamController]].
+  // 5. Let reader be stream.[[reader]].
+  ReadableStreamGenericReader* reader = stream->reader_;
+
+  // 6. If reader is not undefined and reader implements
+  // ReadableStreamBYOBReader,
+  if (reader && reader->IsBYOBReader()) {
+    //   a. For each readIntoRequest of reader.[[readIntoRequests]],
+    ReadableStreamBYOBReader* byob_reader =
+        To<ReadableStreamBYOBReader>(reader);
+    for (ReadableStreamBYOBReader::ReadIntoRequest* request :
+         byob_reader->read_into_requests_) {
+      //     i. Perform readIntoRequest's close steps, given undefined.
+      request->CloseSteps(script_state, nullptr);
+    }
+    //   b. Set reader.[[readIntoRequests]] to an empty list.
+    byob_reader->read_into_requests_.clear();
+  }
+
+  // 7. Let sourceCancelPromise be ! stream.[[readableStreamController]].
   //    [[CancelSteps]](reason).
   v8::Local<v8::Promise> source_cancel_promise =
       stream->readable_stream_controller_->CancelSteps(script_state, reason);
@@ -1747,7 +1765,7 @@ v8::Local<v8::Promise> ReadableStream::Cancel(ScriptState* script_state,
     void CallWithLocal(v8::Local<v8::Value>) override {}
   };
 
-  // 6. Return the result of transforming sourceCancelPromise with a
+  // 8. Return the result of transforming sourceCancelPromise with a
   //    fulfillment handler that returns undefined.
   return StreamThenPromise(
       script_state->GetContext(), source_cancel_promise,

third_party/blink/renderer/core/streams/readable_stream_byob_reader.cc

@@ -33,7 +33,11 @@ void ReadableStreamBYOBReader::ReadIntoRequest::CloseSteps(
     DOMArrayBufferView* chunk) const {
   resolver_->Resolve(script_state,
                      ReadableStream::CreateReadResult(
-                         script_state, ToV8(chunk, script_state), true, true));
+                         script_state,
+                         chunk ? ToV8(chunk, script_state)
+                               : static_cast<v8::Local<v8::Value>>(
+                                     v8::Undefined(script_state->GetIsolate())),
+                         true, true));
 }
 
 void ReadableStreamBYOBReader::ReadIntoRequest::ErrorSteps(

third_party/blink/web_tests/TestExpectations

@@ -3140,10 +3140,8 @@ crbug.com/626703 [ Mac ] external/wpt/streams/readable-byte-streams/non-transfer
 crbug.com/626703 [ Win7 ] external/wpt/streams/readable-byte-streams/non-transferable-buffers.any.serviceworker.html [ Crash ]
 crbug.com/626703 [ Win10.20h2 ] external/wpt/streams/readable-byte-streams/non-transferable-buffers.any.serviceworker.html [ Crash Timeout ]
 crbug.com/626703 [ Mac11.0 ] external/wpt/css/css-counter-styles/counter-style-name-syntax.html [ Failure Timeout ]
-crbug.com/626703 external/wpt/streams/readable-byte-streams/general.any.sharedworker.html [ Timeout ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-015.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-014.html [ Failure ]
-crbug.com/626703 external/wpt/streams/readable-byte-streams/general.any.html [ Timeout ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-001.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-010.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-016.html [ Failure ]
@@ -3154,7 +3152,6 @@ crbug.com/626703 external/wpt/css/css-grid/grid-model/grid-areas-overflowing-gri
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-002.html [ Failure ]
 crbug.com/626703 [ Mac10.14 ] external/wpt/pointerevents/pointerevent_pointercapture_in_frame.html?pen [ Timeout ]
 crbug.com/626703 [ Mac11.0 ] external/wpt/pointerevents/pointerevent_pointercapture_in_frame.html?pen [ Timeout ]
-crbug.com/626703 external/wpt/streams/readable-byte-streams/general.any.worker.html [ Timeout ]
 crbug.com/626703 external/wpt/html/cross-origin-opener-policy/iframe-popup-same-origin-to-unsafe-none.https.html [ Skip Timeout ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-006.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-007.html [ Failure ]
@@ -3171,7 +3168,6 @@ crbug.com/626703 [ Mac ] external/wpt/streams/readable-byte-streams/non-transfer
 crbug.com/626703 [ Win7 ] external/wpt/streams/readable-byte-streams/non-transferable-buffers.any.sharedworker.html [ Crash ]
 crbug.com/626703 [ Win10.20h2 ] external/wpt/streams/readable-byte-streams/non-transferable-buffers.any.sharedworker.html [ Crash Timeout ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-008.html [ Failure ]
-crbug.com/626703 external/wpt/streams/readable-byte-streams/general.any.serviceworker.html [ Timeout ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-011.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-sizing/fit-content-length-percentage-013.html [ Failure ]
 crbug.com/626703 external/wpt/streams/readable-byte-streams/non-transferable-buffers.any.worker.html [ Crash ]