Readable byte stream must call pull if needed after receiving new chunk

After a readable byte stream receives a new chunk from the underlying source, the stream must call pull() (if needed). Otherwise, the stream may get stuck.

Add calls to ReadableByteStreamControllerCallPullIfNeeded at the end of ReadableByteStreamControllerEnqueue and ReadableByteStreamControllerRespondInternal to ensure this.

Fixes #877.

index.bs

@@ -2428,6 +2428,7 @@ nothrow>ReadableByteStreamControllerEnqueue ( <var>controller</var>, <var>chunk<
     1. Assert: ! IsReadableStreamLocked(_stream_) is *false*.
     1. Perform ! ReadableByteStreamControllerEnqueueChunkToQueue(_controller_, _transferredBuffer_, _byteOffset_,
        _byteLength_).
+  1. Perform ! ReadableByteStreamControllerCallPullIfNeeded(_controller_).
 </emu-alg>
 
 <h4 id="readable-byte-stream-controller-enqueue-chunk-to-queue" aoid="ReadableByteStreamControllerEnqueueChunkToQueue"
@@ -2654,6 +2655,7 @@ throws>ReadableByteStreamControllerRespondInternal ( <var>controller</var>, <var
   1. Otherwise,
     1. Assert: _stream_.[[state]] is `"readable"`.
     1. Perform ? ReadableByteStreamControllerRespondInReadableState(_controller_, _bytesWritten_, _firstDescriptor_).
+  1. Perform ! ReadableByteStreamControllerCallPullIfNeeded(_controller_).
 </emu-alg>
 
 <h4 id="readable-byte-stream-controller-respond-with-new-view" aoid="ReadableByteStreamControllerRespondWithNewView"

reference-implementation/lib/readable-stream.js

@@ -1671,6 +1671,8 @@ function ReadableByteStreamControllerRespondInternal(controller, bytesWritten) {
 
     ReadableByteStreamControllerRespondInReadableState(controller, bytesWritten, firstDescriptor);
   }
+
+  ReadableByteStreamControllerCallPullIfNeeded(controller);
 }
 
 function ReadableByteStreamControllerShiftPendingPullInto(controller) {
@@ -1764,6 +1766,8 @@ function ReadableByteStreamControllerEnqueue(controller, chunk) {
     assert(IsReadableStreamLocked(stream) === false);
     ReadableByteStreamControllerEnqueueChunkToQueue(controller, transferredBuffer, byteOffset, byteLength);
   }
+
+  ReadableByteStreamControllerCallPullIfNeeded(controller);
 }
 
 function ReadableByteStreamControllerError(controller, e) {