Reflect recent spec changes to V8 Extra ReadableStream impl

third_party/WebKit/LayoutTests/http/tests/streams/resources/rs-test-templates.js

 'use strict';
 
 // These tests can be run against any readable stream produced by the web platform that meets the given descriptions.
 // For readable stream tests, the factory should return the stream. For reader tests, the factory should return a
 // { stream, reader } object. (You can use this to vary the time at which you acquire a reader.)
 
 self.templatedRSEmpty = (label, factory) => {
   test(() => {}, 'Running templatedRSEmpty with ' + label);
 
   test(() => {
 
     const rs = factory();
 
     assert_equals(typeof rs.locked, 'boolean', 'has a boolean locked getter');
     assert_equals(typeof rs.cancel, 'function', 'has a cancel method');
     assert_equals(typeof rs.getReader, 'function', 'has a getReader method');
     assert_equals(typeof rs.tee, 'function', 'has a tee method');
 
   }, 'instances have the correct methods and properties');
+
+  test(() => {
+    const rs = factory();
+
+    assert_throws(new RangeError(), () => rs.getReader({ mode: '' }), 'empty string mode should throw');
+    assert_throws(new RangeError(), () => rs.getReader({ mode: null }), 'null mode should throw');
+    assert_throws(new RangeError(), () => rs.getReader({ mode: 'asdf' }), 'asdf mode should throw');
+    assert_throws(new TypeError(), () => rs.getReader(null), 'null should throw');
+
+  }, 'calling getReader with invalid arguments should throw appropriate errors');
 };
 
 self.templatedRSClosed = (label, factory) => {
   test(() => {}, 'Running templatedRSClosed with ' + label);
 
   promise_test(() => {
 
     const rs = factory();
     const cancelPromise1 = rs.cancel();
     const cancelPromise2 = rs.cancel();
@@ skipping 583 matching lines @@
       const newReader = stream.getReader();
       return newReader.read();
     });
 
     assert_equals(reader.closed, readerClosed, 'reader.closed is the same after calling read()');
 
     return promise;
 
   }, 'reader\'s closed property always returns the same promise');
 };