Make concept-body use ReadableStream.

This change makes concept-body use ReadableStream instead of readable stream
defined in the encoding spec.

body-readable-stream.md

@@ -0,0 +1,230 @@
+## [Fetch](https://fetch.spec.whatwg.org/) ##
+
+Replace "push" with "enqueue".
+
+Remove __process response body__.
+
+## [Infrastructure](https://fetch.spec.whatwg.org/#infrastructure) ##
+
+To __wait for a response__, if _response_'s body is not null, wait for _response_'s body's stream to be closed or errored.
+
+### [Bodies](https://fetch.spec.whatwg.org/#bodies) ###
+
+A __body__ consists of a ReadableStream object and accompanying data.
+
+A body has an associated stream (a ReadableStream object).
+
+A body has an associated transmitted bytes (an integer). Unless stated it is 0.
+
+A body has an associated total bytes (an integer). Unless stated it is 0.
+
+To clone a body _body_, run these steps:
+
+1. Let «out1, out2» be the result of teeing _body_'s stream. Rethrow any exceptions.
+1. Let _newBody_ be a body whose stream is _out2_ and other members are copied from _body_.
+1. Set _body_'s stream to _out1_.
+1. Return _newBody_.
+
+### [Requests](https://fetch.spec.whatwg.org/#requests) ###
+
+To clone a request _request_, run these steps:
+
+1. Let _newRequest_ be a copy of _request_, except for its body.
+1. If _request_'s body is not null, set _newRequest_'s body to the result of cloning _request_'s body. Rethrow any exceptions.
+1. Return _newRequest_.
+
+### [Responses](https://fetch.spec.whatwg.org/#responses) ###
+
+To clone a response _response_, run these steps:
+
+1. If _response_ is a filtered response, return a new identical filtered response whose internal response is a clone of _response_'s internal response. Rethrow any exceptions.
+1. Let _newResponse_ be a copy of _response_, except for its body.
+1. If _response_'s body is not null, set _newResponse_'s body to the result of cloning _response_'s body. Rethrow any exceptions.
+1. Return _newResponse_.
+
+### [Body mixin](https://fetch.spec.whatwg.org/#body-mixin) ###
+
+Objects implementing the Body mixin gain an associated body (null or a body, initially null).
+
+To __extract__ a body and a \`Content-Type\` value from _object_, run these steps:
+
+1. Let _stream_ be the result of [constructing a ReadableStream object](https://fetch.spec.whatwg.org/#concept-construct-readablestream). Rethrow any exceptions.
+1. Let _Content-Type_ be null.
+1. Switch on _object_'s type: (Same as the original, with replacing "push" with "enqueue").
+1. Close _stream_.
+1. Let _body_ be a body whose stream is _stream_.
+1. Return _body_ and _Content-Type_.
+
+...
+
+An Object implementing the Body mixin is said to be __locked__ if the associated body is not null and its stream is locked.
+
+An Object implementing the Body mixin is said to be __disturbed__ if the associated body is not null and its stream is disturbed.
+
+Objects implementing the Body mixin also have an associated __consume data__ algorithm, with given a _type_, runs these steps:
+
+1. If this object is disturbed or locked, return a new promise rejected with a TypeError.
+1. Let _stream_ be the associated body's stream, if the associated body is not null, or an empty ReadableStream object otherwise.
+1. Let _reader_ be the result of getting a reader from _stream_. If that threw an exception, return a new promise rejected with that exception.
+1. Let _promise_ be the result of reading all bytes from stream with _reader_.
+1. Return the result of transforming promise by a fulfillment handler that returns the result of the package data algorithm with its first argument, _type_ and __MIME type__.
+
+### [Main fetch](https://fetch.spec.whatwg.org/#main-fetch) ###
+
+(20) Otherwise, if _internalResponse_'s body is non-null, run these substeps:
+  1. (Remove)
+  1. Once internalResponse's body has been closed or internalResponse has a termination reason, queue a fetch-done task using _request_ and _response_.
+
+### [HTTP-network-or-cache fetch](https://fetch.spec.whatwg.org/#http-network-or-cache-fetch) ###
+
+Replace the first item by the following.
+
+1. Let _httpRequest_ be _request_ if _request_'s window is "no-window" and _request_'s redirect mode is not "follow", and the result of cloning _request_ otherwise. If that threw an exception, abort these steps and return a network error.
+
+### [HTTP-network fetch](https://fetch.spec.whatwg.org/#http-network-fetch) ###
+
+Add the following after the "Read _request_." sentence.
+
+Run the following substeps:
+
+1. Let _strategy_ be an object. The user agent may choose any object.
+1. Let _pull_ be an action that resumes the ongoing fetch if it is suspended.
+1. Let _cancel_ be an action that terminates the ongoing fetch with reason end-user abort.
+1. Let _stream_ be the result of constructing a ReadableStream object with _strategy_, _pull_ and _cancel_.
+1. Set _response_'s body to a new body whose stream is _stream_.
+
+The subsubsteps in "Whenever one or more bytes are transmitted, let bytes be the transmitted bytes and run these subsubsteps:" should be the following:
+
+1. (Same)
+2. (Same)
+3. (Same)
+4. Enqueue _bytes_ to _stream_.
+5. If _stream_ doesn't need more data and _request_'s synchronous flag is unset, ask the user agent to suspend the ongoing fetch.
+
+### [Request class](https://fetch.spec.whatwg.org/#request-class) ###
+
+In "the Request(input, init) constructor:"
+
+Replace the substeps in the 32th step with the following:
+
+ 1. Let _Content-Type_ be null.
+ 1. Set _temporaryBody_ and _Content-Type_ to the result of extracting a body and \`Content-Type\` value from _init_'s body member. Rethrow any exceptions.
+ 1. (Same)
+
+Replace the substeps in the 35th step with the following:
+
+ 1. Set _input_'s request's body to a new body whose stream is an empty ReadableStream.
+ 1. Let _reader_ be the result of getting a reader from _stream_.
+    Note: This operation will not throw an exception.
+ 1. Read all bytes from _stream_ with _reader_.
+    Note: This operation makes _stream_ disturbed.
+
+The clone() method is defined as follows.
+
+ 1. If this Request object is disturbed or locked, throw a TypeError.
+ 1. Return a new Request object associated with the result of cloning request and a new Headers object whose guard is context object's Headers' guard. Rethrow any exceptions.
+
+### [Response class](https://fetch.spec.whatwg.org/#response-class) ###
+
+Delete the following statements.
+
+- A Response object also has an associated readable stream...
+- A Response object is said to be locked...
+- A Response object's disturbed predicate...
+- A Response object's consume body algorithm,...
+
+The substeps in 7. "If _body_ is given, run these substeps" in Response constructor should be modified as follows.
+
+1. (Same)
+1. Let _Content-Type_ be null.
+2. Set _r_'s response's body and _Content-Type_ to the result of extracting a body and \`Content-Type\` value from _body_. Rethrow any exceptions.
+1. (Same)
+
+The body attribute's getter must return null if the associated body is null and the associated body's stream otherwise.
+
+The clone() method is defined as follows.
+
+1. If this Response object is disturbed or locked, throw a TypeError.
+1. Return a new Response object associated with the result of cloning response and a new Headers object whose guard is context object's Headers' guard. Rethrow any exceptions.
+
+### [Fetch method](https://fetch.spec.whatwg.org/#fetch-method) ###
+
+To process response for response, run these substeps:
+
+1. (same)
+2. Resolve _p_ with a new Response object associated with _response_ and a new Headers object whose guard is "immutable".
+
+To process response end-of-file for _response_, do nothing.
+
+## [XHR](https://xhr.spec.whatwg.org/) ##
+
+### [The send() method](https://xhr.spec.whatwg.org/#the-send()-method) ###
+
+Add the following subsubsteps at the last of "To process response for _response_, run these subsubsteps:"
+
+- If _response_'s body is null, abort these subsubsteps.
+- Let _stream_ be _response_'s body's stream.
+- Let _reader_ be the result of getting a reader from _stream_.
+ - Note: This operation will not throw an exception.
+- Let _read_ be the result of calling ReadFromReadableStreamReader(_reader_).
+ - When _read_ is fulfilled with an object whose done property is false and whose value property is a Uint8Array object, run these subsubsubsteps:
+  - Append the value property to receivedBytes.
+  - If not roughly 50ms have passed since these subsubsteps were last invoked, terminate these subsubsubsteps.
+  - Handle errors for _response_.
+  - If state is headers received, set state to _loading_ and fire an event named readystatechange.
+  - Fire a progress event named progress with _response_'s body's transmitted bytes and _response_'s body's total bytes.
+ - When _read_ is fulfilled with an object whose done property is true, run handle response end-of-file for _response_.
+ - When _read_ is fulfilled with a value that matches with neither of the above patterns, do nothing.
+  - Note: This will not happen.
+ - When _read_ is rejected with an error, handle errors for _response_.
+
+Replace the substeps in the 10th step with the following:
+
+1. (Same)
+1. (Same)
+1. If _response_'s body is null, run handle response end-of-file for _response_ and abort these substeps.
+1. Let _reader_ be the result of getting a reader from _stream_.
+   Note: This operation will not throw an exception.
+1. Let _promise_ be the result of reading all bytes from _response_'s body with _reader_.
+1. wait for _promise_ to be resolved or rejected.
+ - If _promise_ is resolved with _bytes_, append _bytes_ to receivedBytes and run handle response end-of-file for _response_.
+ - If _promise_ is rejected, run handle error for _response_.
+
+To process response end-of-file for _response_, run handle response end-of-file for _response_ if _response_'s body is null.
+
+### [Response](https://xhr.spec.whatwg.org/#xmlhttprequest-response) ###
+
+An XMLHttpRequest object has an associated receivedBytes (a byte sequence). Unless stated otherwise it is an empty byte sequence.
+
+### [Response body](https://xhr.spec.whatwg.org/#response-body) ###
+
+An __arraybuffer response__ is the return value of these steps:
+
+1. (Same)
+2. Set response ArrayBuffer object to a new ArrayBuffer object representing receivedBytes and return it.
+
+A __blob response__ is the return value of these steps:
+
+1. (Same)
+2. (Same)
+3. Set response Blob object to a new Blob object representing receivedBytes and return it.
+
+A __document response__ is the return value of these steps:
+
+1. (Same)
+2. If response's body is null, return null.
+3. Let _bytes_ be a byte stream containing receivedBytes.
+(The original algorithm follows...)
+
+A __JSON response__ is the return value of these steps:
+1. (Same)
+2. If response's body is null, return null.
+3. Let _bytes_ be a byte stream containing receivedBytes.
+(The original algorithm follows...)
+
+A __text response__ is the return value of these steps:
+
+1. If response's body is null, return the empty string.
+2. Let _bytes_ be a byte stream containing receivedBytes.
+(The original algorithm follows...)
+