static unsafeGetArrayBuffer_(view) {
    if (!ArrayBuffer.isView(view)) {
      return /** @type {!ArrayBuffer} */(view);
    } else {
      return /** @type {!ArrayBufferView} */(view).buffer;
    }
  }
Gets the underlying ArrayBuffer of the given view.  The caller needs to
ensure it uses the "byteOffset" and "byteLength" fields of the view to
only use the same "view" of the data.

@param {BufferSource} view
@return {!ArrayBuffer}
@private