[Not ready for review] Add Streams API support to FileReader

LayoutTests/http/tests/xmlhttprequest/response-stream-partial-chunk-expected.txt

Index: LayoutTests/http/tests/xmlhttprequest/response-stream-partial-chunk-expected.txt
diff --git a/LayoutTests/http/tests/xmlhttprequest/response-stream-partial-chunk-expected.txt b/LayoutTests/http/tests/xmlhttprequest/response-stream-partial-chunk-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..55a481ff7371b5c581b22ec5ec9fd624c6ddb8af
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+++ b/LayoutTests/http/tests/xmlhttprequest/response-stream-partial-chunk-expected.txt
@@ -0,0 +1,20 @@
+Test partial data is readable from Stream returned by XMLHttpRequest.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS xhr.response is null
+PASS xhr.status is 200
+PASS onloadstart invoked on reader
+PASS reader.result is non-null.
+PASS reader.readyState is reader.LOADING
+PASS reader.error is null
+PASS result[0] is 'Hello'.charCodeAt(0)
+PASS result[1] is 'Hello'.charCodeAt(1)
+PASS result[2] is 'Hello'.charCodeAt(2)
+PASS result[3] is 'Hello'.charCodeAt(3)
+PASS result[4] is 'Hello'.charCodeAt(4)
+PASS successfullyParsed is true
+
+TEST COMPLETE
+