Thread-safe HTTP transport for Google App Engine based on URL Fetch.
Implementation is thread-safe. For maximum efficiency, applications should use a single
globally-shared instance of the HTTP transport.
URL Fetch is only available on Google App Engine (not on any other Java environment), and is
the underlying HTTP transport used for App Engine. Their implementation of HttpURLConnection is simply an abstraction layer on top of URL Fetch. By implementing a
transport that directly uses URL Fetch, we can optimize the behavior slightly, and can
potentially take advantage of features in URL Fetch that are not available in HttpURLConnection. Furthermore, there is currently a serious bug in how HTTP headers are
processed in the App Engine implementation of HttpURLConnection, which we are able to
avoid using this implementation. Therefore, this is the recommended transport to use on App
Engine.
