Code: void MultibufferDataSource::StartCallback() {
  DCHECK(render_task_runner_->BelongsToCurrentThread());

  if (!init_cb_) {
    SetReader(nullptr);
    return;
  }

  bool success = reader_ && reader_->Available() > 0 && url_data() &&
                 (!assume_fully_buffered() ||
                  url_data()->length() != kPositionNotSpecified);

  if (success) {
    {
      base::AutoLock auto_lock(lock_);
      total_bytes_ = url_data()->length();
    }
    streaming_ =
        !assume_fully_buffered() && (total_bytes_ == kPositionNotSpecified ||
                                     !url_data()->range_supported());

    media_log_->SetDoubleProperty("total_bytes",
                                  static_cast<double>(total_bytes_));
    media_log_->SetBooleanProperty("streaming", streaming_);
  } else {
    SetReader(nullptr);
  }

  base::AutoLock auto_lock(lock_);
  if (stop_signal_received_)
    return;

  if (success) {
    if (total_bytes_ != kPositionNotSpecified) {
      host_->SetTotalBytes(total_bytes_);
      if (assume_fully_buffered())
        host_->AddBufferedByteRange(0, total_bytes_);
    }

     media_log_->SetBooleanProperty("single_origin", single_origin_);
    media_log_->SetBooleanProperty("passed_cors_access_check",
                                   DidPassCORSAccessCheck());
     media_log_->SetBooleanProperty("range_header_supported",
                                    url_data()->range_supported());
   }

  render_task_runner_->PostTask(FROM_HERE,
                                base::Bind(std::move(init_cb_), success));

  UpdateBufferSizes();

  UpdateLoadingState_Locked(true);
}

Vulnerability Type: Bypass 
CWE ID: CWE-732
Summary: Service works could inappropriately gain access to cross origin audio in Media in Google Chrome prior to 71.0.3578.80 allowed a remote attacker to bypass same origin policy for audio content via a crafted HTML page.
Commit Message: Simplify "WouldTaintOrigin" concept in media/blink

Currently WebMediaPlayer has three predicates:
 - DidGetOpaqueResponseFromServiceWorker
 - HasSingleSecurityOrigin
 - DidPassCORSAccessCheck
. These are used to determine whether the response body is available
for scripts. They are known to be confusing, and actually
MediaElementAudioSourceHandler::WouldTaintOrigin misuses them.

This CL merges the three predicates to one, WouldTaintOrigin, to remove
the confusion. Now the "response type" concept is available and we
don't need a custom CORS check, so this CL removes
BaseAudioContext::WouldTaintOrigin. This CL also renames
URLData::has_opaque_data_ and its (direct and indirect) data accessors
to match the spec.

Bug: 849942, 875153
Change-Id: I6acf50169d7445c4ff614e80ac606f79ee577d2a
Reviewed-on: https://chromium-review.googlesource.com/c/1238098
Reviewed-by: Fredrik Hubinette <hubbe@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598258}