Use SimpleQueue in WritableStream implementation

Split out Queue into a separate file from ReadableStream and rename is
SimpleQueue to reduce the risk of name collisions on the binding object.

Add a peek() method as it is needed by WritableStream.

Modify WritableStream to use SimpleQueue.

BUG=681493

Review-Url: https://codereview.chromium.org/2752133003
Cr-Commit-Position: refs/heads/master@{#458324}
4 files changed