[BreakoutBox] Replace MSTP::is_pending_pull_ with a counter

|is_pending_pull_| was used to make sure that frames were made available
to the stream only if there was a pending pull request.

However, if multiple pull requests are issued and then no more pull
requests arrive, some of the corresponding read requests will remain
unsettled when |is_pending_pull_| becomes false.

This CL fixes this by replacing the boolean |is_pending_pull_| with a
counter.

Bug: 1218120
Change-Id: I0ffc038a73a6cd1d387dc17e9c21f2c62fc50613

lint.ignore

@@ -814,3 +814,5 @@ DUPLICATE-BASENAME-PATH: dom/nodes/ParentNode-querySelector-All-content.html
 DUPLICATE-BASENAME-PATH: dom/nodes/ParentNode-querySelector-All-content.xht
 DUPLICATE-BASENAME-PATH: svg/struct/reftests/reference/green-100x100.html
 DUPLICATE-BASENAME-PATH: svg/struct/reftests/reference/green-100x100.svg
+
+SET TIMEOUT: mediacapture-insertable-streams/MediaStreamTrackProcessor-video.https.html

mediacapture-insertable-streams/MediaStreamTrackProcessor-video.https.html

@@ -45,6 +45,48 @@ <h1 class="instructions">Description</h1>
                      [processor.readable]);
   return promise;
 }, "Tests that the reader of a video MediaStreamTrackProcessor produces VideoFrame objects and is closed on track stop while running on a worker");
+
+function makeVideoFrame() {
+  const canvas = new OffscreenCanvas(100, 100);
+  const ctx = canvas.getContext('2d');
+  return new VideoFrame(canvas);
+}
+
+promise_test(async t => {
+  // The generator will be used as the source for the processor to
+  // produce frames in a controlled manner.
+  const generator = new MediaStreamTrackGenerator('video');
+  // Use a larger maxBufferSize than the default to ensure no frames
+  // will be dropped.
+  const processor = new MediaStreamTrackProcessor({track: generator, maxBufferSize:10});
+  const reader = processor.readable.getReader();
+  const writer = generator.writable.getWriter();
+
+  let numReads = 0;
+  let resolve = null;
+  const promise = new Promise(r => resolve = r);
+
+  const numOperations = 4;
+  // Issue reads without waiting for the frames to arrive.
+  for (let i = 0; i < numOperations; i++) {
+    reader.read().then(dv=> {
+      dv.value.close();
+      if (++numReads == numOperations)
+        resolve();
+    });
+  }
+
+  // Write video frames in different tasks to "slowly" settle the pending read
+  // requests.
+  for (let i = 0; i<numOperations; i++) {
+     await writer.write(makeVideoFrame());
+     await new Promise(r=>setTimeout(r,0));
+  }
+
+  return promise;
+
+}, "Tests that multiple read requests are eventually settled");
+
 </script>
 </body>
 </html>